Optoelectronic and other com- Ponents sometimes use a thermo-electric cooler and a thermistor for temperature control. A typical thermoelectric cooler has 1A maximum current and 1Ω impedance. These parameters make simple series-pass drive circuits inefficient, given the typical available supply voltages (5,12, or 15V). Often, several thermoelectric coolers exist in a single circuit (for example, a multiple-wavelength optical transmitter). In this case, you can obtain improved efficiency by using the circuit in Figure 1. This circuit has three devices to cool, so it contains three coolers and three thermistors. On the sensor side, each thermistor connects to a standard proportional-integral-differential op-amp or μP-based-controller , circuit. Each controller produces a command voltage that is proportional to the current its respective cooler requires.
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