BJT Transistor Bias Voltage Calculator

The Formulas

The main formulas used in BJT bias calculations are:

\[I_B = \frac{V_{CC} - V_{BE}}{R_B}\] \[I_C = \beta \times I_B\] \[V_{CE} = V_{CC} - (I_C \times R_C)\]

Where:

• IB: Base current
• IC: Collector current
• VCC: Supply voltage
• VBE: Base-Emitter voltage (typically 0.7V for silicon BJTs)
• VCE: Collector-Emitter voltage
• RB: Base resistor
• RC: Collector resistor
• β (beta): Current gain of the transistor

Calculation Steps

1. Calculate the base current (IB) using the supply voltage, base-emitter voltage, and base resistor
2. Calculate the collector current (IC) using the base current and current gain
3. Calculate the collector-emitter voltage (VCE) using the supply voltage, collector current, and collector resistor

Example Calculation

Let's calculate the bias voltages for a BJT with these parameters:

• VCC = 12V
• RB = 100kΩ
• RC = 1kΩ
• β = 100
• VBE = 0.7V (assumed)

1. Calculate IB:

\[I_B = \frac{12V - 0.7V}{100k\Omega} = 113\mu A\]

2. Calculate IC:

\[I_C = 100 \times 113\mu A = 11.3mA\]

3. Calculate VCE:

\[V_{CE} = 12V - (11.3mA \times 1k\Omega) = 0.7V\]

This example demonstrates how to use the calculator to determine the operating point of a BJT in a simple bias circuit.