BJT Cascode Amplifier Calculator

This BJT Amplifier calculator calculates bias voltages and currents, gains, and frequency responses for the Cascode amplifier. Enter values of Cascode amplifier and hit the “Compute” button to use this online calculator for computing bias voltage and current levels, gain and frequency response for the Cascode amplifier.

BJT Cascode Amplifier Calculator

R1(K ohms)

V_C1 (Collector Voltage)(V)

R2(K ohms)

V_E1 (Emitter Voltage)(V)

R3(K ohms)

V_B1 (Base Voltage)(V)

R_C (Collector resistor)(K ohms)

V_C2 (Collector Voltage)(V)

R_E1 (Emitter resistor, AC bypassed)(K ohms)

V_E2 (Emitter Voltage)(V)

R_E2 (Emitter resistor, gain control)(ohms)

V_B2 (Base Voltage)(V)

VP (Supply Voltage)(V)

I_C (Collector Voltage)(mA)

Beta (DC Current Gain)

I_B (Base Voltage)(mA)

V_BE (Base to emitter drop)(V)

g_m (Transconductance)

R_s (Source Resistance):(ohms)

r_π(Input Resistance of BJT at low freq)(ohms)

R_L (Load resistor)(ohms)

R_IN (Input Resistance of Amp)(K ohms)

f_T (Current Gain BW Product):(MHz)

A (Amplifier Voltage Gain)

C_CB (Cu Collector-Base Cap.):(pF)

f₁(MHz)

C_BE (C_π, Base-Emitter Cap.): Optional(pF)

f₂(MHz)

BW(MHz)

Equations

V_B1= R3/(R1+R2+R3)

V_B2= (R2+R3)/(R1+R2+R3)

V_E1= V_B1-V_BE

V_E2= V_B2-V_BE

V_C1= V_E2

V_C2= VP - I_C*R_C

R_B1= R3*(R1+R2)/ (R1+R2+R3)

I_B*R_B1 + I_B*Beta*R_E+V_BE=V_B1

I_B= (V_B1-V_BE)/(R_B1+Beta*R_E)

I_C= Beta*I_B

g_m= Ic/25mA

r_π=Beta/g_m

If RE2 is zero ohms:

A= -g_m*((RL||RC)*(R2||R3))/(R23+RS)*(r_π/(r_π+Rx+(R2||R3||RS)),

else

A= -(RL||RC)/RE2

Rx is typically10-30 ohms, we use 20 in the calculator.

f_T= g_m/(2π*(C_BE+C_BC))

f₁= 1/(Rin*(Cbe+ 2*Ccb))/(2*π);

f₂= 1/(R_L*Ccb)/(2*π);

The lower pole is dominate:

BW= f₁;

BJT Cascode Amplifier Calculator Overview

The BJT Cascode Amplifier Calculator is an advanced online tool designed to assist engineers and enthusiasts in calculating essential parameters for BJT Cascode amplifiers. This tool simplifies the process of determining bias voltages, currents, gain values, and frequency responses for this type of amplifier, making design and analysis much easier.

What is a BJT Cascode Amplifier?

A Cascode amplifier is a two-stage circuit that combines a common emitter amplifier and a common base amplifier. This configuration is popular for its ability to provide high gain and extended bandwidth, while overcoming limitations such as Miller capacitance that affect traditional amplifier designs.

In practical terms, the BJT Cascode Amplifier excels in high-frequency applications due to its ability to handle larger bandwidths and its improved stability in the signal path.

Key Features of the Calculator:

Accurate Biasing Calculations: Automatically calculates the bias voltages and currents for both transistors in the Cascode configuration.
Gain Estimation: Helps you determine the gain of the amplifier based on the input parameters like resistances and transistor characteristics.
Frequency Response: Provides an estimate of the amplifier’s bandwidth and frequency response, accounting for factors like Miller capacitance and buffer stages.
User-Friendly Interface: Simple and intuitive input fields for resistances, capacitances, and transistor parameters.

Why Use a Cascode Amplifier?

High Gain: The Cascode amplifier offers a significantly higher gain than traditional amplifiers.
Wide Bandwidth: By overcoming the Miller effect, it achieves much wider bandwidth, making it suitable for RF tuners and other high-frequency applications.
Improved Stability: The second transistor in the common base stage helps stabilize the amplifier’s operation.

Applications:

RF circuits and tuner designs
High-frequency amplifiers in communication systems
Amplitude modulation circuits using the Cascode configuration for signal processing.

With the BJT Cascode Amplifier Calculator, designing and analyzing these amplifiers becomes much more straightforward, enabling both professionals and hobbyists to create efficient, high-performance circuits.