Creating a Voltage Transfer Characteristic (VTC) for a Zener Diode Circuit

[foobag]

http://img847.imageshack.us/img847/1922/capturevq.jpg

I need help starting this.

So far I am getting Voh = +10V from the zener diode, and Vol = -10V, the upper and lower saturation limits based on the zener diodes

Then for threshold values I am getting an upper threshold Vth = -R1/R2 * Vol = 6.25 V

and a lower threshold as Vtl = - R1/R2* Voh = -6.25V

does this seem logical for the VTC for the first part?

Whats the point for R3 in this circuit other than protection of the zener diodes, does it/will it play effect on my calculations?

 

[vk6kro]

When you put zeners in series, one behaves like a zener and the other behaves like a diode, depending on the polarity. So, you get a Zener voltage plus 0.7 volts in each direction.

However, if you assume that this is a total of 10 volts, then your result looks OK.

The function of the Zeners would be to stabilize the Schmitt triggering point, which otherwise depends on the supply voltage.
The 2 K resistor gives a predictable current into the Zeners. It also limits this current.

It doesn't come into the gain calculation, though, because you get 10 volts across the Zeners, regardless of gain.

 

[foobag]

thanks a lot for your help! it makes more sense now

 

[foobag]

does anyone know what part I can use in PSPICE/ORCAD for use as a double anode zener diode?

 

[DeeNos]

Your initial calculations for the upper and lower saturation limits and threshold values seem to be on the right track. The voltage transfer characteristic (VTC) for a Zener diode circuit is a plot of output voltage (Vout) vs input voltage (Vin). It is used to show the relationship between the two and how the circuit responds to changes in the input voltage.

R3 in this circuit serves as a load resistor for the Zener diodes. It helps to regulate the current flowing through the diodes and ensures that they are operating within their safe operating limits. It also helps to stabilize the output voltage by providing a path for the current to flow through when the Zener diodes are conducting. In terms of your calculations, R3 may affect the output voltage slightly, but it should not have a significant impact on the overall VTC.

To create a VTC for this circuit, you will need to vary the input voltage (Vin) and measure the corresponding output voltage (Vout). This can be done by using a variable power supply or by manually adjusting the input voltage with a potentiometer. You can then plot the data points on a graph and connect them to create the VTC curve.

It is important to note that the VTC for a Zener diode circuit may not be a perfectly straight line, as the diodes have a non-linear response. The curve may also differ slightly depending on the specific characteristics of the diodes used in the circuit.

Overall, creating a VTC for a Zener diode circuit is an important step in understanding its behavior and ensuring that it is operating within its desired parameters.