JFET Ohmic Resistance Calculation
This question asks us to find the ohmic resistance of a JFET (Junction Field-Effect Transistor) given specific parameters: the pinch-off voltage, denoted as \(V_p\), and the drain current when the channel is fully on (zero gate-source voltage and saturation), denoted as \(I_{DSS}\).
Understanding JFET Ohmic Resistance
The ohmic resistance (or zero-bias resistance) of a JFET is typically the resistance between the drain and source terminals when the device is operating in the linear (or triode) region with zero gate-source voltage (\(V_{GS} = 0\)). This is often referred to as \(R_{DS(on)}\) when \(V_{GS}=0\).
A common approximation used to estimate this resistance relates the pinch-off voltage and the saturation drain current.
Formula for Ohmic Resistance
The formula used for calculating the approximate ohmic resistance (\(R_{DS(on)}\)) when \(V_{GS} = 0\) is:
$ R_{DS(on)} \approx \frac{V_p}{I_{DSS}} $- \(V_p\) is the pinch-off voltage.
- \(I_{DSS}\) is the drain current when \(V_{GS} = 0\) and the JFET is in saturation.
Applying the Formula
We are given the following values:
- Pinch-off Voltage, \(V_p = 4V\)
- Drain Current at Saturation (\(V_{GS}=0\)), \(I_{DSS} = 10mA\)
First, ensure the current is in Amperes:
$ I_{DSS} = 10mA = 10 \times 10^{-3} A = 0.01 A $Now, substitute these values into the formula:
$ R_{DS(on)} \approx \frac{4V}{0.01 A} $Performing the calculation:
$ R_{DS(on)} \approx 400 \ \Omega $Result
Therefore, the ohmic resistance of the JFET under these conditions is approximately 400 Ohms.
Important Questions from Operation of JFET
A junction Field Effect Transistor can operate in
In a junction field effect transistor the depletion layer width at a distance x from the source is:
Which of the following statements are correct for an N channel FETs?
A. N channel FET has larger electron mobility than P channel FETs.
B. N channel FET has electrons as current carriers.
C. N channel FET has more noise than P channel FET.
D. N channel FET has larger transconductance than P channel FETs.
Choose the correct answer from the options given below:
