Small signal approximation diode model

[Bolterx101]

hello all I am new here so i don't know if this is the correct place for this topic so sorry for any inconvenience caused.

this is my question:
Use the small-signal model of the diode to predict the output voltages for the input voltages given. Plot a graph of | vout(t) | based on the small signal model.

Input Voltage 1 = 0.65 + 0.04cos(2*pi*200*t) V
Input Voltage 2 = 0.68 + 0.01cos(2*pi*200*t) V
0 ≤ t ≤ 20ms

i know vout = -Is*R*exp(vin/Vt)

How would you solve this? what basically is the small signal model? is it like a formula that I have to substitute these values in? And for the graph what goes on the x-axis and what goes on the y-axis?

I've got a diagram of the circuit if it helps for you to see:
http://www.flickr.com/photos/24949707@N07/3430348460/

Thank You.

 

[Redbelly98]

Welcome to Physics Forums ... and sorry about the delayed response.

This explains the small-signal model for diodes:
http://en.wikipedia.org/wiki/Diode_modelling#Small-signal_modelling

For Input 1 you'll need to figure out:

• The diode current when V_diode = 0.65V
• dI/dV for the diode, when V_diode = 0.65V

Use that information to get a linear relation between I and V, that is the small-signal model for the diode.

 

[Mene]

Dear user,

The small signal approximation diode model is a simplified model used to analyze the behavior of a diode in response to small changes in input voltage. It is based on the assumption that the diode is operating in the forward biased region and the input voltage is small enough that the diode's exponential relationship between voltage and current can be approximated as linear.

To solve this problem, you can use the small signal model equation you provided, vout = -Is*R*exp(vin/Vt), and substitute in the given values for the input voltages and time. The small signal model is essentially a formula that relates the output voltage to the input voltage and diode parameters.

For the graph, the x-axis would be time (t) and the y-axis would be the absolute value of the output voltage (|vout(t)|). You can use a graphing calculator or software to plot the graph based on the equation and given values.

I hope this helps answer your questions. Good luck with your analysis!