An integrated circuit junction capacitor is formed using conventional bipolar transistor technology. Voltage variable capacitance is provided by a reverse biased emitter-base junction and parasitic collector-base capacitance is isolated from the emitter-base capacitance by maintaining the base-collector...http://www.google.com.au/patents/US4191899?utm_source=gb-gplus-sharePatent US4191899 - Voltage variable integrated circuit capacitor and bootstrap driver circuit
