This application note describes the use of thermal techniques in measurement and control circuits. By utilizing the relationship between temperature and electronic devices, it is possible to find solutions to difficult circuit design problems.
The document explains how to utilize thermal parasitics in circuitry rather than just eliminating them. It details the design of a precision temperature controller for small component ovens using thermistors and pulse width modulation to manage heater power efficiently.
Additionally, the note covers specific applications such as logarithmic signal conditioning for PIN photodiodes over a 100dB range and a high-bandwidth thermal RMS-to-DC converter capable of handling waveforms up to 50MHz.
The 2kHz pulse width modulated heater power is much faster than the thermal loop's response.
The circuit responds logarithmically to light inputs from 10nW to 1mW.
The converter achieves wide bandwidth performance up to 50MHz.