CIRCUIT MULTIVIBRATEUR

摘要

In an astable multivibrator circuit, a diode operates in conjunction with a voltage supply derived from the multivibrator output signal to insure the initiation of oscillations by limiting base drive current to the multivibrator transistors when power is first applied. This prevents saturation of both transistors and ensures sufficient loop gain to initiate oscillations in response to an unbalance in the system. As power is first applied, the diode is non-conductive and a relatively low voltage is applied to bias the multivibrator transistors. During normal operation, the voltage derived from the multivibrator output signal causes the diode to conduct, thereby coupling the base circuits to the operating potential supply. While conductive, the diode forward voltage drop compensates for changes in the Vbe of the transistors due to temperature variations and tends to maintain a constant charging current for the base circuits.