The circuit presented uses two common transistors and is powered by the circuit being tested. The circuit is for TTL logic, since its supply is 5 V.
This amplifier has a few Watt output, using old transistors. The speaker is 45 ohms, but with...
This circuit is from a 1965 Motorola manual. It can be implemented with a common 2N2646 and a 106...
This circuit, in addition to transforming a sinusoidal signal into a square, shifts its phase. The...