A temperature setpoint circuit comprises bipolar transistors Q1 and Q2 which receive currents I1 and I2 at their respective collectors and are operated at unequal current densities, with a resistance R1 connected between their bases such that the difference in their base-emitter voltages (.DELTA.V.sub.be) appears across R1. An additional PTAT current I3 is maintained in a constant ratio to I1 and I2 and provided to the collector of Q2 while Q2 is off, and is not provided while Q2 is on. The circuit is arranged such that Q2 is turned on and conducts a current equal to Ia when:.DELTA.V.sub.be=(kT/q)ln(NI1/Ia), where Ia=I2+I3, the temperature T at which .DELTA.V.sub.be=(kT/q)ln(NI1/Ia) being the circuit's setpoint temperature, such that the switching of current I3 provides hysteresis for the setpoint temperature which is approximately constant over temperature.