Diode Circuits

Voltage Regulation

RectifierCircuit

Tin

Half-Wave Rectifier

Cause of ripple: the capacitor is discharged for almost an entire period.

inversion

Ripple Reduction: Do not allow the capacitor to discharge so frequently

An Inverting Half-Wave Rectifier

If Vin >0, D1 and D2 are off.If Vin <0, D1 and D2 are on and Vout>0.

An Non-Inverting Half-Wave Rectifier

If Vin >0, D1 and D2 are on, Vout>0.If Vin <0, D1 and D2 are off.

Full-Wave Rectifier

Inverting

Non-Inverting

Full-Wave RectifierAlternative Drawing

Inverting Non-InvertingFull-Wave A.K.A. Bridge Rectifier

Using Constant Voltage Diode Model

Vout=-Vin-2VD, on Vout=Vin-2VD, on

Input versus Output

|Vin|<2VD,on

Addition of the Smoothing Capacitor

Modification of Ripple Estimation Formula

Modification:1.Turn-on voltage2.1/2 to account for inversion of negativepeaks.

Maximum Reverse Voltage

VB=VD,on

VA=VP

VAB=VP-VD,on

Maximum reverse voltage is approximately Vp

Vp is the amplitude of Vin

Compare Maximum Reverse Bias Voltage to Half-Wave Rectifier

A reverse diode voltagemust sustain larger reverse bias voltage

Currents as a function of time

Application of Bridge Rectifier

Summary

Application of Limiting Circuits

Limit the signal amplitude at a suitable point in the receiver

Characteristic of a Limiting Circuit

A Simple Limiter

General Limiter Circuit

Application of Voltage Doubler

Electronic systems typically provide a global supply voltage: 3V

Design of some circuits will be simplified if they from a higher supply voltage.

Voltage Doubler

Floating Capacitor Capacitor Divider

Capacitor Diode CircuitIdeal diode. Vout pinned to 0 V

Positive charges begin to leave the leftPlate of C1, turning D1 off.

C1 is now a floating capacitor

Generating 0 to 2Vp Waveform

Peak Detector

Voltage Doubler

Peak Detector0 to 2Vp waveform

Diode as a Voltage Shifter

Application:

We may need to shift the average level of a signal up and down because the subsequent stage (e.g. an amplifier) may not operate properly with the present dc level.

A Simple Level Shift

Shift up the DC by 2 VD, On

A simple electronic switch

CK is 1: I1=1, diodes are shorted, and Vin=Vout.

CK is 0,diodes are off, charges are storedacross C1.