This high-impedance headphone circuit was found in a 1990s William Sheets. The power is low, but the high input impedance makes it useful for radio applications.
Available at Mouser Electronics this component of Diodes Incorporated consists of a voltage...
Found in Radio Electronics this circuit uses a fotodiac to drive a triac. The circuit can use...
The first circuit was suggested by Analog Devices (www.analog.com) in its Application Note AN-411...