I did exactly that for a log amp about 10 years ago. Used a MAT-04 with one transistor as the temp sensor, 2 transistors as the heaters and the
4th as the log element. The circuit was actually from Jim Williams. I used 1/2 AD708 as the heater driver and the other half as a lamp driver. The LED is red when under temp and turns green at temperature. Using multiple meters on the unit as temp readout and drive level, placing a finger on the package causes the drive to increase with no measurable change in the temp monitoring point. IIRC 469 mV corresponds to 69 C. From room temp to operate takes 10-15 seconds. The heaters run on 12 volts with the drive limited to 30mA to not damage the transistors during initial warm up. Actual maintenance current is only a few mA when warmed up. GG