We found this circuit in the 1964 RCA transistors manual. The transistors used are uncommon today, but they can be used equivalent. The circuit controls the operation of a heating element.
To obtain a signal with a variable mark / space ratio in a ratio of 1 to 20 to 20 to 1, we have...
Other operational amplifiers series, such as the MC34072, MC34074, MC35071, MC35072, MC35074 d...
We found this sophisticated meter circuit in an article in Radio Electronics magazine from June...