Op Amp Regulator
Posted on Dec 30, 2012 11631
This op amp offers a straightforward method of developing a single-polarity stable voltage source (see the figure). TVansi
stor Ql gets a base drive through resistor Rl, and conducts to develop a voltage (Vi) across the IC"s supply pins. Amp Al, R2, and Ql form a positive-feedback closed loop, along with R3 and the zener diode. Al, R2, and Ql also form a negative-feedback closed loop with R4 and R5. The effect of positive feedback is predominant as the noninverting input receives Vx while the inverting input receives only: This happens until the zener comes into play. When the voltage at the inverting input exceeds the voltage at the noninverting input, Al"s output takes away Ql"s base current through R2, which reduces Vi. Hence, an equilibrium condition is reached. Now: This circuit can source more than 30 mA.