Category: Fet Biasing

Biasing FET Switching Circuits

Biasing FET Switching Circuits: JFET Switching – A Biasing FET Switching Circuits is normally in an off state with zero drain current, or in an on state with a very small drain-source voltage. When the FET is off, there is a drain-source leakage current so small that it can almost always be neglected. When the […]

MOSFET Biasing Circuits

MOSFET Biasing Circuits: DE-MOSFET Bias Circuits – DE-MOSFET bias circuits are similar to JFET bias circuits. Any of the FET bias circuits already discussed can be used to produce a negative VGS level for an n-channel MOSFET Biasing Circuits, or a positive VGS for a p-channel device. In this case, both devices would be operating in […]

Universal Transfer Characteristics for FET

Universal Transfer Characteristics for FET: A Universal Transfer Characteristics for FET is simply a transfer characteristic plotted with IDSS = 1 and VP = 1. Then, instead of the scales being calibrated in milliamps and volts, they are marked as the ratios ID/IDSS and VGS/VP. To construct the Universal Transfer Characteristics for FET, Eq. 9-1 is rewritten, Now, by substituting […]

JFET Biasing Circuits

JFET Biasing Circuits: Use of Plus/Minus Supplies – When plus/minus supply voltages are to be used with a JFET Biasing Circuits, the gate terminal is usually grounded via RG, as illustrated in Fig. 10-40(a). In this case, the circuit is essentially a voltage divider bias circuit with the gate bias voltage equal to the level […]

JFET Bias Circuit Design

JFET Bias Circuit Design: Design Approach – Design of JFET Bias Circuit Design is just as simple as design of BJT bias circuits. One major difference is that FET circuit design normally uses a graphical approach involving the drawing of a bias line on the device transfer characteristics, as in the case of FET circuit […]

JFET Bias Circuit Troubleshooting

JFET Bias Circuit Troubleshooting: Voltage Measurement – JFET Bias Circuit Troubleshooting are similar to those for BJT bias circuits. The major difference is that there is only one junction in the FET (the gate-channel junction) that might become short-circuited or open-circuited. To determine if the circuit is functioning correctly, the FET terminal voltages should all […]

Basic JFET Biasing Circuits Comparison

Basic JFET Biasing Circuits Comparison: The Basic JFET Biasing Circuits Comparison (gate bias, self-bias, and voltage divider bias) are similar in performance to the three basic BLIP bias circuits, (base bias, collector-to-base bias, and voltage divider bias). Comparing the performance of FET bias circuits, it should be recalled that each FET type number has maximum […]

Voltage Divider Bias Circuit

Voltage Divider Bias Circuit: For the self-bias circuit, it was seen that increasing the resistance of RS brings ID(max) and ID(min) closer together, but that increased RS values result in lower ID levels. As will be demonstrated, Voltage Divider Bias Circuit allows RS to be increased without making ID very small. Figure 10-17 shows that a voltage […]

Self Bias Circuit Diagram

Self Bias Circuit Diagram: Circuit Operation – In a self bias JFET circuit, gate-source bias is provided by the voltage drop across a resistor in series with the device source terminal. Consider the n-channel JFET Self Bias Circuit Diagram illustrated in Fig. 10-11. The voltage drop across resistor RS is,   If ID = 1 mA and RS […]

Gate Bias Circuit

Gate Bias Circuit: Circuit Operation – Consider the Gate Bias Circuit shown in Fig. 10-6. The FET gate terminal is connected via resistor RG to a bias voltage VG. If the gate is directly connected to the bias source (instead of using RG), any ac signal applied to the gate would be short-circuited to VG. […]