This variable filter that lets frequencies from 500 Hz to 1500 Hz pass through was found in a Popular Electronics from the 90's. The operational amplifiers are the 741.
Suggested by Siliconix in documentation from the 90s, this amplifier has its gain digitally...
This circuit is from Radio Electronics. The magazine no more exists, but the circuit can be...
An oscillator that uses two gates is not suitable for critical applications, as it tends to pick...