---
title: "Precision rectifier circuit"
subject: "Electronics Devices and Circuit"
chapter: 5
key: "semester_3/electronics_devices_and_circuit:precision-rectifier-circuit"
source: https://www.bctengineer.com/q/semester_3/electronics_devices_and_circuit/precision-rectifier-circuit
site: BCT Engineering
---

# Precision rectifier circuit

Electronics Devices and Circuit · Chapter 5: Signal Generator and Waveform-Shaping Circuits

- Asked in: 2081 Baisakh, 2 marks
- Video: [What is Precision Rectifier? Precision Rectifier Explained](https://www.youtube.com/watch?v=5HweBajP-5g) — ALL ABOUT ELECTRONICS
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_3/electronics_devices_and_circuit/precision-rectifier-circuit
- Whole chapter: https://www.bctengineer.com/md/semester_3/electronics_devices_and_circuit/chapter-5

## Question

Draw the circuit diagram of precision rectifier circuit.

## Short answer

A precision half‑wave rectifier places diodes inside an op‑amp’s feedback loop to eliminate diode drop. In the inverting version, for negative inputs Vo = –(Rf/R) Vin, for positive inputs Vo = 0; a non‑inverting version gives Vo = Vin for Vin>0.

## Answer

A precision (super-diode) half-wave rectifier uses an op-amp with the diodes inside its feedback loop, so that it rectifies voltages smaller than the diode drop.

#### Circuit diagram (inverting half-wave type)
```text
                +---------[ Rf ]----------+
                |                         |
                |     D1                  |
                +-----|>|------+          |
                |              |          |
 Vin o---[ R ]--+--(-)\        |    D2    |
                       >-------+---|>|----+-----o Vo
           GND ----(+)/                   |
                                        [RL]
                                          |
                                         GND
```

- D1 (anode at the inverting node, cathode at the op-amp output) conducts for positive Vin. It keeps the loop closed, and the output is Vo = 0.
- D2 (anode at the op-amp output, cathode at Vo) conducts for negative Vin, and Vo = −(Rf/R) Vin, which is a positive half-wave.

Non-inverting alternative: a single diode in series with the output of a voltage follower, with the feedback taken from the cathode side of the diode and a load resistor to ground: Vo = Vin for Vin > 0 and 0 otherwise.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. Why can a precision rectifier rectify signals smaller than the diode drop?
   A. The diode is placed inside the op-amp feedback loop
   B. It uses a Schottky diode only
   C. It uses a transformer
   D. The input is amplified first by 100
   Answer: A. The op-amp's high gain compensates for the diode drop when the diode is in the feedback loop. (Key point: Purpose)

2. In the inverting half-wave type, what is Vo when D2 conducts (negative Vin)?
   A. Vo = Vin
   B. Vo = -(Rf/R) Vin
   C. Vo = 0
   D. Vo = Rf Vin
   Answer: B. With D2 on, the circuit is an inverting amplifier, giving a positive output. (Key point: Inverting circuit output)

3. What does D1 do for positive Vin?
   A. Conducts to keep the loop closed so Vo = 0
   B. Blocks and saturates the op-amp
   C. Doubles the output
   D. Charges a capacitor
   Answer: A. D1 conducting keeps the feedback loop closed and the output at zero for positive input. (Key point: Role of D1)

## Related in Electronics Devices and Circuit

- [Precision half wave rectifier](https://www.bctengineer.com/question.md?key=semester_3%2Felectronics_devices_and_circuit%3Aprecision-half-wave-rectifier) — Electronics Devices and Circuit, chapter 5, asked 5×
- [Full wave bridge rectifier load power](https://www.bctengineer.com/question.md?key=semester_3%2Felectronics_devices_and_circuit%3Abridge-rectifier-power-5ohm) — Electronics Devices and Circuit, chapter 6
- [Unregulated dc supply with bridge rectifier](https://www.bctengineer.com/question.md?key=semester_3%2Felectronics_devices_and_circuit%3Aunregulated-bridge-power-supply) — Electronics Devices and Circuit, chapter 6

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