Means for controlling temperature rise of temperature stabilized substrates

Claim 1

IN AN AUTOMATIC TEMPERATURE CONTROL CIRCUIT FOR A TEMPERATURE STABILIZED SUBSTRATE OR THE LIKE COMPRISING A PLURALITY OF SENSING DIODES IN HEAT EXCHANGE RELATIONSHIP WITH THE SUBSTRATE AND CONNECTED IN SERIES WITH A RESISTANCE ACROSS A REFERENCE VOLTAGE FOR PRODUCING A VOLTAGE AT THE JUNCTION BETWEEN THE DIODES AND THE RESISTANCE PROPORTIONAL TO THE TEMPERATURE OF THE DIODES, A TRANSISTOR AMPLIFIER HAVING AN INPUT COUPLED TO THE JUNCTION BETWEEN THE DIODES AND THE RESISTANCE AND AN INVERTING OUTPUT, AND HEATER MEANS HAVING AN INPUT COUPLED TO THE OUTPUT OF THE AMPLIFIER FOR HEATING THE SUBSTRATE IN PROPORTION TO THE OUTPUT OF THE AMPLIFIER, THE IMPROVEMENT COMPRISING: A TRANSISTOR THE COLLECTOR OF WHICH IS CONNECTED TO A SUPPLY VOLTAGE, THE BASE OF WHICH IS CONNECTED TO THE OUTPUT OF THE AMPLIFIER, AND THE EMITTER OF WHICH IS CONNECTED TO THE SERIES OF DIODES AT A POINT SUCH THAT THE NUMBER OF DIODES BETWEEN THE EMITTER AND THE INPUT OF THE AMPLIFIER RESULTS IN A MAXIMUM VOLTAGE OF THE OUTPUT OF THE AMPLIFIER SUFFICIENTLY LOW TO LIMIT THE OUTPUT OF THE HEATER MEANS TO A SAFE LEVEL WHEN THE DIODES ARE RELATIVELY COLD AND SUCH THAT THE NUMBER OF DIODES BETWEEN THE EMITTER AND THE REFERENCE VOLTAGE PROVIDES A SUFFICIENTLY GREATER VOLTAGE DROP WHEN THE DIODES ARE COLD TO PLACE THE EMITTER OF THE TRANSISTOR AT A POTENTIAL SUCH THAT THE BASE-EMITTER OF THE TRANSISTOR WILL FORWARD BIASED AND A SUFFICIENTLY SMALL VOLTAGE DROP WHEN THE DIODES APPROACH THE STABILIZED TEMPERATURE THAT THE BASE-EMITTER JUNCTION OF THE TRANSISTOR WILL BE REVERSE BIASED.