Variable gain oven temperature control circuit

The frequency of an electronic oscillator is controlled by a crystal located in the oven. The heaters in the oven include resistance elements for quick warm-up, and steady state. The circuit allows the quick warm-up power to be reduced incrementally as the set temperature is approached and effects a smooth transition to the steady-state heater. This is accomplished by circuit features which reduce the control loop gain when high power is applied to the heaters and increase the gain as the warm-up power decreases.