Integrated injection logic time-base oscillator circuit - uses constant current source and large switched current to produce large swing linear sawtooth voltage across capacitor

摘要

The oscillator consists of a capacitor and an integrated current injection logic module. It contains a transistor which forms a switch with a current input from a current source whilst the emitter is connected to a common point (5). One injection logic module (A) is connected to the output of a controlled current generator along with the capacitor (10). The common point (5) is connected to the negative supply through a resistor (R1). The current generator consists of a fixed current generator (14) a current mirror (T4,T5). The control transistor is connected to the common point or to a potentiometric tap on the supply resistor. Other modules are connected in the circuit to produce a relaxation oscillator or monostable with a linear sawtooth voltage across the capacitor with a wide voltage swing. The logical and analogue components are realised using the same technology. The time base circuit is used to use two current generators one giving a fixed current and the other a much larger current. The larger one is switched on and off to periodically charge and discharge the capacitor with a sawtooth voltage.