This simple injector and signal follower employs a high impedance headset. Transistors can be of general use. The circuit is from old American documentation.
The original document is from Philips, but now available from NXP (www.nxp.com) which is the...
In the figure we show how to implement a voltage-controlled oscillator. The circuit is from Texas...
Three LM158, LM258, LM358, or LM2904 operational amplifiers are used in this instrumentation amplifier....