Preamplifier with Several Gains (CB933E)

The transistors of this circuit may be the BC548 or BC549 and its power supply can be performed with voltages from 15 to 22 V. The circuit has a gain determined by the values of the components in the feedback circuit. The input connections and signal output should be shielded. Consumption is very low, on the order of a few milliamperes. If a power supply is used, it must have excellent filtration. The level of the output signal is of the order of a few hundred millivolts, enough to excite the input of most audio amplifiers. Input is average impedance. C has values between 4n7 and 47 nF.




GAIN 10 20 30 40 DB
R1 4k7 1,5 k 1,5 k 1 k Ω
R2 12 15 56 180
R3 470 560 330 680 Ω
R4 1,8 2,2 2,2 2,2
R5 1,2 k 470 270 220 Ω

Circuit Bench