This simple circuit has good gain and can be implemented with any general-purpose transistor. The circuit is from Electronics Now, June 1997. The coil determines the frequency range.
This configuration with the LM111 was found in your factory manual. The circuit can be implemented with...
The double T of this circuit makes it amplify only the 1 kHz signals. The circuit can be used as a...
This car alarm was obtained in a Signetics documentation from the 1980s. The circuit uses the 555...