This 1 kHz circuit was found in American documentation from the 90s. The original operational amplifier consists of a double 741 at the time. The power supply must be symmetrical.
This commercial receiver from the year 1958 uses two AA cells as Power supply. The circuit is...
PIC18F “K40” Features Intelligent ADC with Filtering and Signal Analysis Capabilities Ideal for...
This circuit appears in similar versions on this site. This is from a Popular Electronics from the 80's. The...