Transistor measuring instrument circuit b

Figure a is a simple transistor tester circuit. It can measure the collector-base
reverse current IeLo and penetration current j of PNP and NPN low-power transistors . and common-emitter current amplification coefficient
    circuit description: Sl is a double-pole double-throw switch, which can be used to measure PNP and NPN transistors. Flip this switch to reverse the positive and negative thresholds of
  power supply El. S2 is a four-pole four-throw switch composed of S21, S22, S23, and S24. The following takes the PNP type as an example to explain the circuit for
  measuring k, Iceo and J9.
    1) To measure the J buckle, turn S2 to position 1. The circuit is as shown in Figure b. At this time, the transmitter terminal is open circuit, the collector terminal is connected to the negative terminal of the power supply, and
  the base terminal is connected to the positive terminal of the power supply. The resistor is a current-limiting resistor to prevent the current meter from being damaged by incorrect wiring or by inserting a transistor that has broken down.
  The ammeter can choose the 100-500mA range. Since the I of the low-power germanium tube is 1-10yA and the silicon tube is below 10A, the ammeter pointer
  only deflects slightly.
    2) To measure k, turn S2 to position 2. The circuit is as shown in Figure c. At this time, the base is open circuit, the collector is connected to the negative pole of the power supply, and the emitter is
connected to the positive pole of the power supply. The resistor is a current limiting resistor. j of low power germanium tube. From a few microamps to hundreds of microamps, j of silicon tubes. Below a few microamps
. The ammeter can choose the L00-500mA range.
    3) p-[yJ measurement - first turn S2 to position 3, the circuit is as shown in Figure d. At this time, resistor R2 and variable potentiometer RP1 are connected in series to form a bias
resistor. -Adjusting RP1 can make the transistor collector current from a few tenths of a milliampere to several tens of milliamperes. The ammeter can be selected from 5 to 10 mA.
The measured Lu value changes due to different collector currents. The collector current can be selected according to the purpose of the transistor. For example, for frequency conversion and mid-range amplifier,
you can use 0. 5-lmA, for low-current transistor, you can use 1-2mA, for push-pull, you can use s-10mA, etc. j．
  4) After the collector current is adjusted. Turn sz to position 4, and the circuit is as shown in Figure e. At this time, the power supply E2 gives the current
meter a reverse current lp through Rs and RP2. Adjusting RP2 can make j. -I. , the pointer of the ammeter points to zero.
    Finally press the normally open button switch S3. Through R, the base gets the base current increment Ah. Alb-6V/3Mfl=2tLA. After
amplification by the transistor, the collector also obtains the collector current increment A1. . At this time, the pointer of the ammeter deflects, and its reading is the collector current increment
Alc. The current amplification coefficient can be obtained from the following formula
    p = AI. /AIh
  measurement is completed, first change the ammeter to 5-10mA level to protect the current source, then turn S2 back to position 1, and then unplug the transistor .