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How does an operational AMP work with a Zener diode?
Well, when our input is positive (Vi>0) , the output Vo is negative (Vo<0), so Zener diode conducts but both D1 and D2 are reversed biased,so the circuit works as an inverting operational amplifer with Gain=-Rf/Rin=-10K/1K=-10. So Vo=-10Vi. I am a bit confused with the other case about the negative input (Vi<0).
What kind of transistor is used for Zener?
As a voltage reference, the Zener diode D1 is used, and a PNP transistor (Q1) is used to regulate the output voltage. To achieve the stability of the output voltage, this voltage is fed back to the non-inverting input of the operational amplifier, through the resistor R4.
What is the reverse leakage of the Zener diode?
For reverse voltages below the zener voltage, you’d expect the zener diode to be OFF and essentially out of the circuit. Unfortunately, a small current leaks across the diode defined by the IS parameter in the diode model. For the 1N746, the reverse leakage is specified at I LEAK = 5 μA.
How is the output of an op amp maintained?
The inverting input of the operational amplifier is maintained at 5.1 V by means of the zener diode (D1). If the output voltage of the power supply drops, the voltage at the op-amp’s non-inverting terminal also drops, as well as the op-amp output.
What kind of biasing voltage do I need for op amp?
For op-amp circuits operating from the +3.3-V standard, a +1.65-V biasing voltage is needed. Zener diodes are commonly available only down to +2.4 V, although the 1.225-volt AD589 and AD1580 bandgap shunt regulators can be used like Zener diodes to provide a fixed—though not centered—voltage at low impedance.
Are there problems with a capacitive coupled non inverting amplifier?
Though apparently simple, there are problems with it. Illustrating the problem, the circuit of Figure 1, which has several design weaknesses, is an ac-coupled non-inverting amplifier. The signal is capacitively coupled in and out.
How to avoid instability in single supply amplifier?
A non-inverting single-supply amplifier using Zener-diode biasing. A Zener should be chosen that has an operating voltage close to V S /2. Resistor R Z needs to be selected to provide a high enough current to operate the Zener at its stable rated voltage and to keep the Zener output noise low.