This is a combined circuit of tone generator and preamplifier. We found it in a 1975 documentation. Operational amplifiers of that time can be replaced by modern equivalents.
This circuit can operate with signals up to 60 MHz using the indicated operational. We found it in...
National Semiconductor suggests the figure circuit for stabilizing the peak value of an...
We found this circuit in a 1980 documentation. With basic changes, including transistors that were...