Maker Factory ELECTRONICS EXPERIMENTS BOX Manual page 259

Circuits 45 and 46: The two transistors ensure that current of 5 mA flows through the Zener diode Z, regard-
less of the voltage value of the Zener diode. The moving-coil instrument needle indicates the value of the
Zener voltage.
Fig. 3.44: Circuit 44:
Two-stage AF pream-
plifier
Fig. 3.45: Circuit 45:
Meters for 4.7 V Zener
diodes and higher
261