7. Transistor ···············································
7.2 Basic operation of transistor ···················
7.2.1 Basic operation of NPN type transistor
This type has been connected in opposite case to PNP type ; but in this NPN type, as shown in figure below, a few holes are supplied from positive pole of electric source so that these make a small portion current of base current IB. And electrons that come from emitter as not having been
able to join with base holes move to collector side owing to VCB of collector side so that these make
collector current IC. Ordinarily 95~98 % among emitter current IE becomes IC but remainder 2 ~5 %
becomes IB. Current Ib Emitter(E) Base(B) Vbe NPN type Vcb Current Ic Collector(C)
Forward bias of NPN type transmitter: Emitter's electron most moves by collector
Ib [uA]
Ic [mA]
<Base electric current and collector electric current> P
Type
N type
PNP type transmitter structure & symbol > Collector(C ) P Type Emitter (E) Base (B) Collector(C ) Emitter (E) Base (B) Collector(C ) Emitter (E) Base (B) N Type P type
NPN type transmitter structure & symbol N Type Base (B) Emitter (E) Collector(C )
7.2.2 Basic operation of PNP type transistor
If forward voltage VBE is applied between emitter and base, electric potential barrier in between PN
junction surface becomes low. And at P type side of emitter side, many holes are being generated because impurity material concentration has been heightened, And as for base N side, because this is very thin so that impurity material concentration becomes lower, there are only few electrons.
Accordingly holes in emitter cross over the electric potential barrier and enter the base side by diffusion so as to vanish by bonding with a part of base electrons there. But because these few electrons are continuously supplied by negative “-“ pole of electric source, these make the small base current IB.
If backward voltage VC B is applied between base and collector, electric potential barrier is heightened
at PN junction surface so that electric current does not flow between base and collector.
Holes that could not join with base electrons but come from emitter now move to collector side owing to VCB of collector side. These make collector current IC. Emitter holes are gradually supplied from
positive pole so that these make emitter current Ic. Accordingly most IE becomes IC but very little
portion becomes base current IB.
7.2.3 Amplification function of transistor
As we have already discussed above in `Basic Operation', most electron (no less than 95 %) move to collector but only a few electrons (no more than 5 %) join with base hole. So as electron current and electric current direction are ordinarily defined oppositely while emitter current
I
E is divided into collector current IC and base currentI
B, the following equation holds :C B
E
I
I
I
Like this, big collector current may be deduced from small base current so as to be called electric current amplification while relationship (ratio) between
I
B and IC are called electric current amplification factor (hF E).For calculation example, if
I
B is 1 mA and IC is 100 mA then hF E is 100. Namely it meansB C
I
I
hFE
,100
1
100
Meanwhile in how to use transistor, there are three earth methods of emitter earth, base earth and collector earth among which the emitter earth method as in circuit above is most used.
.
And generally amplification means that of alternating current component , which we shall deliberate in the following example :
In circuit shown in figure here, if AC signal is applied between base and emitter, base current
I
B flows only when it is in forward direction (same as in diode). Whence collector current IC also appears as output while being amplified only of half wave. Namely transistor does not operate during negative (-) half cycle because here it is in backward direction between base and emitter.Here let us apply DC between base and emitter. If AC is applied onto DC, AC component is added upon DC so as to appear like what is shown in the following figure.
Ic=100mA Ib=1mA B E C hFE=100 Input (Ib=uA) Output (Ic=mA) B E C Input Output
Voltage at this time is called bias voltage. Now for the first time we can see completely amplified output waveform. Also we may obtain the amplified AC waveform only if we remove DC component by connecting a condenser at output terminal.
To avoid inconvenience of using two electric supplies due to bias voltage as in the depicted circuit , actual circuits use various forms adequate to purpose of each circuit by such as an electric current feedback bias, a fixed bias using a resistance, condenser etc. on the supply electricity source connected to the output terminal..
*
For reference to say, there is limit area where collector current does not increase any more eventhough transistor base current continues to increase so as to be called the saturation region. Accordingly transistor 's amplification action is accomplished only in specific area where collector current increases in accordance with base current increase so as to be called the active area .
So far we have learned electric current amplification but now let us think case of voltage amplification . According to the above explanation, we learned that collector varies proportionately with base current . Let us think this as a variable resistor to control electric current . Then we can think the following equivalent circuit . Input (Ib=uA) B E C Input Output Bias voltage Output (Ic=mA)
Under condition as above, output voltage to the base input waveform shows up reversely as may be seen in figure. It is explained as total voltage E = voltage drop between collector and emitter (Eo) + voltage drop due to resistance R (Ic × R). Namely, if electric current Ic increases, voltage drop due to resistance R also increases so that the output voltage Eo decreases. (Output voltage Eo = E – (Ic × R)) Output (Eo) R E Current Ic B E C Current Ic Output (Eo) R E <Equivalent circuit> Output Current (Ic=mA) Output voltage (Eo=E-(Ic*R) Input current (Ib=uA)
Now let us learn base earth and collector earth methods along with transistor 's switching action .
Base earth circuit
Method of base earth is type of circuit as shown in figure to take base as earth and apply input signal to emitter.
If there is no electric potential difference between emitter and base, emitter current does not flow as well as their flows no electric current at collector where voltage is applied in backward direction through resistance. If forward voltage is applied between emitter and base as in circuit shown by figure, collector current may also flow through resistance.
In this case, because sum of base current and collector current is equal to emitter current , ratio of collector current to emitter current is below 1 so that electric current is not amplified.
In case of voltage amplification, if we suppose for example that 10mA flows in emitter, then some 1mA and 9mA flows in base and collector respectively so that voltage drop occurs, through resistance, in collector that is the output .
Accordingly it becomes 9mA × resistance [kΩ] = output voltage so there is accomplished voltage amplification to the input signal .
B E
C
Input
Output
Collector earth circuit
Method of collector earth is type of circuit as shown in figure to take collector as earth , send input signal to base and send output from emitter.
In emitter earth circuit , collector current greatly varies according to base current while variation of value of load resistance connected to collector does not give large effect to electric current . But in collector earth circuit , because forward voltage is applied between emitter and base for output circuit , emitter current (from collector to emitter) flows so as to be applied at load resistance as it is .
Accordingly emitter current is controlled by small base current as well as emitter current varies directly also by load resistance variation .
As above, we learned three types of earth methods according to terminals used in common . Among them the most general and usually used method is emitter earth method whereas to summarize it may be explained by the following characteristics table.
.
Characteristic of earth methods
Item Emitter Earth
Circuit Base Earth Circuit
Collector Earth Circuit
Electric current
amplification degree High Low Mid
Voltage amplification High Mid Low
Electric power amplification High Mid Low
Input impedance Mid Low High
Output impedance Mid High Low
Phase of output to input Antiphase Inphase Inphase
High frequency
To understand amplification circuit that use transmitter
Circuit description
- The R1's resistance changes NPN transistor base and bias that is approved to emitter voltage to 3 volts. There is serving resistance
- Variable resistor is thing to control NPN transistor's bias voltage by 0 ~ 3 volt
- That is, become transistor's base and emitter bias voltage high if variable resistance value is high, and resistance value two. If is low, bias voltage becomes low
- Therefore flowing electric current is passed much to collector and emitter according to bias voltage - Therefore, can control turning number of motor according to position of variableness resistance
passing as motor's electric current by bias voltage differs.
I
E
I
BI
C B CI
I
h F E
hFE:The electric current amplification rate, IB:Base current, Ic:Collector current) R1=1㏀ 12V D235 (NPN TR) 1~100Ω variable resistor Base Emitter Collector M Motor
7.2.3 Switching function of transmitter
In explanation of amplification action, we learned that if to electrify between emitter and collector, it would do making the base current Ib to flow. Namely it will do if we supply base current up to saturation state where collector current will not almost increase any more. (Nevertheless in small signal amplification circuit or ordinary home appliances, usually use is made of amplification action not in saturation region but in active area . ) We can turn on / off circuit between emitter and collector by on / offing the base current Ib under this condition . This is called transistor 's switching action among transistor 's amplification action..
We can make role like of relay if using transistor 's switching action as shown in figure.
Transistor 's base current corresponds to relay 's excitation current so that transistor may act as the relay while not using mechanical contact as in relay 's contact point . And if load increases then electric current Ic also increases, whereas, when we cannot supply sufficient electric current by a transistor, we can make use of electric current amplification by means of connecting transistors in multistage in accordance to load capacity.
So transistor 's switching action has the following advantages to the relay. - Switching speed is fast (more than thousand times per second).
- Operation is stable and there is no chattering when on / offing the contact point as that in relay because there is no mechanical contact . It is small type with less electric power consumption . It has longer life than mechanical relay.
Batt
ON/OFF input signal
Load Switching relay B E C Current Ic Batt ON/OFF Input signal Load Switching transmitter
To understand transistor switching circuit
1. In below circuit, when ignition key switch does ON, power is supplied to the ignition coil. 2. If supply power to power TR Base from ECM through Pin No23 ignition coil of electric
current passes by ground G11.
3. Again ECM transmitter's base power when coil's electric current is shut off because connection between collector and emitter becomes open if do Off in coil high tension generate become.
From ignition key switch
Pin No 23 Ground G11
7.3 Judgment of good / b ad transistor
As may be seen in figure, it will be fine if we think transistor to have been connected with part of emitter and base considered as a PN junction diode and part of base and collector considered as another diode..
1. When multi-meter measures between B~E and B~C in forward direction under normal condition, it is electrified ( showing ordinarily some hundred mV in case of digital meter but a low resistance value in case of analog type meter). Inversely when measured in reverse direction, it is not electrified so that there is little change in indication value of multi-meter (by which there is displayed a voltage same as for case when measuring rod was not connected in case of digital meter while there is displayed an approximately infinite resistance value is displayed in case of analog meter).
2. Next if also measured for interval of E~C forwardly and backwardly with the measuring rod, there is little change in indication value of multi-meter for both of the reciprocal cases because it is not electrified for both cases. Whereas in some cases according to transistor sort and characteristic when red (+) rod is connected to collector and black (-) rod is connected to emitter (in case of NPN, but reversibly in case of PNP), quite a high resistance value may be displayed even though it would not be infinite ( so namely a little current may flow).
For reference to say, when testing transistor or diode, if measuring under condition where it has been connected to circuit , it may be affected by connected circuit resistance value, it is desirable to
measure under condition isolated from circuitry. And in case where generally transistor or diode has been broken , it is displayed as primarily short circuit form .
Base Base Collector Emitter NPN Transmitter Base Emitter Collector
Polarity distinction of transistor
1. In case of using analog multi-meter.
1) Put mode switch in Analog multi meter at R100 or R1000 with in measurable range. 2) First connect a lead wire to any pin in transistor. Then connect left 2 terminals in
transistor respectively, using other lead wire.
3) At this moment, if the direction becomes CW, which resistance measuring becomes nearly OΩ, black lead wire connection becomes base line in NPN transmitter and red lead wire connection becomes base line in PNP transmitter.
4) If you set mode switch in R1000 at circuit tester, result in CW direction after measuring other two pins’ resistance respectively, red lead wire connection becomes collector in NPN and black lead wire becomes collector in PNP.
Multi Meter Multi Meter
Base
1 2 3
1 : Collector 2 : Emitter 3 : Base
2. In case of find polarity to use transistor's lead wire.
When saw flat side that printed of part name.
In case of 2SC1815 transistor (NPN type transistor for high frequency)
- Right side lead : Base - Center side lead : Collector - Left side lead : Emitter
Emitter Base Collector Base Collector Emitter
In case of 2SD880 transistor (NPN type transistor for high frequency)
- Right side lead : Emitter - Center side lead : Collector - Left side lead : Base
8. Thermistor
To semiconductor element that use change of resistance according to temperature, there are NTC thermistor and PTC thermistor
8.1 NTC (Negative Temperature Coefficient) thermistor)
- Characteristic
If temperature rises, there is characteristic that resistance decreases
- Usage in car
Engine coolant temperature sensor, Air intake temperature sensor, and Low fuel-warning sensor Temperature
Resistance
- To understand circuit usage PTC thermistor.
NPN transistor's bias voltage depends on NTC thermistor in below circuit If temperature rises, voltage between base and emitter is raised.
Therefore, TR does ON and lamp turned “ON”.
8.2 PTC (Positive Temperature Coefficient) thermistor)
- Characteristic
If temperature rises, there is characteristic that resistance increases - Usage in car
Central door lock actuator
- To understand circuit that use NTC thermistor. In below circuit, lamp turned ON when switch ON.
If excess current is passed to ramp, heat by excess current is occurred to thermistor At this time, thermistor's resistance increases and decreases electric current. Therefore, prevent over current in circuit.
NPN TR 12 Volts Battery Lamp R1 NTC Thermistor Battery Lamp Thermistor Switch
9. Photoconductive cell
According to brightness of light, value of resistance changes.(increase or decrease) . Material that convey light is Cds (Cadmium sulfide) and CdSe (Cadmium selenide) - Characteristic
Resistance decreases if brightness of light is strong, and there is Characteristic that resistance increases if light becomes feeble
- Usage in car
Auto light sensor, FATC air conditioning system - To understand circuit that use CDS
1) If transmitter1 does ON, lamp turned ON. 2) For TR1 does ON, TR2 must do ON
3) TR2's ON operates according to cds's resistance value 1 10 100 1,000 Lux KΩ 10,000 1,000 100 10 1
10. Piezo-electric element
If receive pressure, if electromotive force happen, and supplies voltage, there is special quality that cause transformation
- Material : Titan acid, Barium - Usage in car : Knock Sensor - Knock sensor waveform
a. Cylinder Pressure Signal
b. Filtered Cylinder Pressure Signal c. Knock Sensor Signal
R1=10㏀ R4=4.7 ㏀ R2=4.7㏀ R3=1㏀ cds Lamp NPN TR1 2SC372 12 volts BATT. NPN TR2 2SC372
Circuit that use Photoconductive cell
11. Hall effect
When you put hall IC in magnetic field at concentric position with current flowing, both hall IC end can produce some voltage.
In the following picture, if you put any conduct in magnetic field and make some current flow through this, A1 and A2 can produce some voltage out.
If you simulate the magnetic field then the output voltage between A1 and A2 becomes on and off. When tone wheel destroy the magnetic filed the output voltage between A1 and A2 in the following picture, becomes on. When this tone wheel reaches without any damage to the magnetic field the output voltage becomes off
A1
A2
Iv
- Usage in car
CMP sensor, CKP sensor, Speed sensor ect.
- Signal waveform
Time Volt
12. Integrated Circuit (I.C)
12.1 Integrated circuit general
An integrated circuit or IC is several hundreds of resistors, transistors and other elements formed on a substrate to function as if they were single device. When reading a circuit with an IC, understanding of the operating conditions as indicated by the timing chart or table is important. In this chapter, how a circuit with an IC should be read will be described.
Type of I.C
Classification by Scale of Integration
○ SSI (Small Scale Integrated Circuit) : Less than 100 elements ○ MSI (Medium Scale Integrated Circuit) : 100 to 1,000 elements ○ LSI (Large Scale Integrated Circuit) : 1,000 to 100,000 elements ○ VLSI (Very Large Scale Integrated Circuit) : 100,000 or more elements
Classification by Application and Structure
▣ Analog IC I.C amplifying or controlling analog quantity (continuous quantity) Output signal always changes linearly with the input signal This type of IC’s is widely used in units using analog circuits.
▣ Digital IC I.C that performs switching only. According to input ON/OFF signal conditions, the output is obtained as ON/OFF switching signal.
Features of I.C.
○ Size reduced to minimum by integration ○ High reliability thanks to integrated structure ○ Low price thanks to volume production ○ Low power consumption
12.2 Analog I.C
The IC shown here is one called comparator.
“a” is the power supply terminal and “b” is the ground terminal, both are required to supply power to the comparator for its operation but are not directly associated with the operation itself.
The comparator compares the potential at terminal c and terminal d and in this operating conditions shown, it gives output va[v] at point e only when the potential at point c is higher than the potential at point d.
Of the two input terminal voltages, one that remains constant is called the reference voltage and one that changes is called the comparison voltage which of the two input terminals has the reference voltage can be known from the circuit connected to the comparator.
＋ + c d － ＋ c A (Va) b (Vb) Vc Vd Operating conditions
Output(Va volt) is made when Vc＜Vd Output(Va volt) is not made when Vc≤Vd
12.3 Digital I.C
Logic circuit
In a digital circuit, two signals are used, that is, signal with high voltage (H) and signal with low voltage (L) or presence of signal and absence of signal.
And as a convention, these two signals are represented by “1” and “0”.
For example, when the transistor is off in this figure, Vce is 12V and this state of voltage is taken as