Nuts and Volts - August 2013

the walkie-talkies), I included it in the schematic. However, I think there is enough gain for the system to work without the transformer.

The first stage is a “long tail pair” which has wide bandwidth and low distortion, but the voltage swing is limited due to the necessity to bias the bases. Q3 is an emitter-follower driving the Q4 grounded base. The signal at Q5 can swing nearly rail to rail, but with some distortion.

The bias is highly dependent on the transistor beta (hfe), so you will need to tweak R16 to get between 4 and 4. 5 volts at the collector. Q2 is an NPN which is not as common as PNP in germanium; Q1 and Q2 should be complementary pairs. AC128 (PNP and AC127 (NPN) have been suggested for the output transistors; you can find them on eBay. In Figure 7, I wanted to simulate the audio transformer, which required some guesstimates. If the high impedance side is rated