Can a Diode be used as a Resister 1

[joinnow]

Can a diode be used as a resistor?if yes then how if no then what are the problems.Please help.Thanks in advance

 

[automatic2]

if your need is voltage dropping then a diode may emulate a resistor. A resistor provides proportionate voltage change in response to current change. A diode provides a consistent voltage drop in response to changing current. The difference in devices is not as important as to there role within the circuit.

 

[Lewish]

A diode can be used as a voltage step reduction. Every diode is slightly different and the voltage drop across each is a function of the amount of current flowing thru the diode.

For example, a diode I use a lot is a BAV99. At 1ma the voltage drop across it is 0.715 volts. At 10ma it is 0.855 volts. At 50ma it is 1.000 volts. And at 150ma the voltage drop is 1.250 volts.

This should give you an understanding of using diodes to reduce your voltage. I use them this way in lots of designs.

 

[IRstuff]

There is another consideration, which is that a standard signal diode is one-directional, e.g., in the reverse bias configuation, there is negligible conduction.

As an expansion to the previous diode comments, the diode current is proportional to Is*exp(Vd/kT), so if you need a one-directional nonlinear resistor, a diode is the ticket. TTFN

 

[melone]

Why don't you tell us what you application is, and we can suggust whether or not a diode will yield acceptable results (and why).

 

[benno]

Have you considered a zener diode. A zener, can set a rail voltage very accurately and in a reverse biased configuration behaves in a similar (not exact) way to a resistor in circuit. Ben Roberts

Broadcast Engineer

Sentient being.

 

[dumbo]

Jfets with the gate tied and mosfets are used as variable resistors fundimental to digital control.

 

[melone]

BENNO, be very careful with your accuracy statement. Measure the zener voltage over temperature.

 

[BrianR]

A forward biased diode is a non-linear resistor at low currents. It acts as a battery of about 0.6V in series with a resistor, rd.

rd(ohms) ~= 26mV/Id(mA) at room temperature, and has a negative temp coefficient of -2.2mV/degC for silicon.

Example if the diode forward current = 1mA, then rd ~= 26ohms and at 0.1ma it = 260 ohms.

These are approximations but quite close enough for most work.

 

[ambertec]

At RF and microwave frequencies, PIN diodes are used as variable resistances for gain control.