This 3-decade operating range VCO was found in a 90s Popular Electronics. The circuit uses components that admit of equivalents.
This circuit is from a Japanese publication in 1967. The circuit uses a Geiger-Muller valve and...
Motorola's LM13600 integrated circuit is not very common today. The input voltage is 10 mV. We...
This circuit is from a 70s linear integrated manual. The integrated circuit used is uncommon today...