Emitter Follower Design Calculator

About the Emitter Follower Design Calculator

The Emitter Follower Design Calculator is a powerful tool for designing emitter follower circuits, which are widely used in audio and signal processing applications. See how emitter follower circuit is also used in the AM demodulation circuit and phase shifting circuit. This calculator simplifies the process of determining key component values (resistors and capacitors) to ensure optimal performance of the circuit within the desired frequency range.

How It Can Be Useful

1. Precision Design :
   The calculator ensures accurate calculations for resistor and capacitor values, minimizing errors in manual computations.

2. Time-Saving :
   Instead of performing complex calculations manually, users can quickly obtain results by entering a few parameters.

3. Versatility :
   It supports various units for inputs (e.g., Hz, kHz, MHz for frequency; Ω, kΩ, MΩ for resistors), making it adaptable to different design requirements.

4. Wide Applications :
   The emitter follower circuit is commonly used in:

   • Audio Signal Processing : Buffering signals from microphones or audio amplifiers.
   • Impedance Matching : Ensuring efficient signal transfer between stages.
   • Tone Control Circuits : Preserving signal integrity while adjusting frequency response.

Where It Can Be Used

• Audio Systems : To buffer signals from electret microphones or drive headphones.
• Signal Conditioning : In preamplifier stages for sensors or communication systems.
• Educational Purposes : For students and hobbyists learning about transistor circuits and their applications.
• DIY Electronics : For building custom audio equipment, such as guitar pedals or mixers.

Example Calculation

Input Parameters :

• Supply Voltage (Vcc): 15 V
• Quiescent Current (Iq): 1 mA
• Transistor Gain (β): 100
• Cutoff Frequency (fc): 20 Hz (selected as "Hz")
• Resistor R2: 150 kΩ (selected as "kohm")
• Load Impedance (ZL): 10 kΩ

Step-by-Step Calculation :

1. Calculate Emitter Voltage (Ve) :
   $Ve=0.5\times Vcc=0.5\times 15=7.5\text{V}$

2. Calculate Emitter Resistor (Re) :
   $Re=\frac{Ve}{Iq}=\frac{7.5}{1\times 10^{-3}}=7.5\text{kΩ}$

3. Calculate Base Voltage (Vb) :
   $Vb=Ve+0.65=7.5+0.65=8.15\text{V}$

4. Calculate Input Impedance (Zin) :
   $Zin=\beta \times Re=100\times 7.5\times 10^3=750\text{kΩ}$

5. Calculate Output Impedance (Zout) :
   $Zout=\frac{Zin}{10}=\frac{750\times 10^3}{10}=75\text{kΩ}$

6. Calculate Resistor R1 :
   $R1=\left(\frac{Vcc-Vb}{Vb}\right)\times R2=\left(\frac{15-8.15}{8.15}\right)\times 150\times 10^3\approx 128.3\text{kΩ}$

7. Calculate Capacitor C1 :
   $Rp=\frac{R1\times R2}{R1+R2}=\frac{128.3\times 10^3\times 150\times 10^3}{128.3\times 10^3+150\times 10^3}\approx 70.9\text{kΩ}$
   $C1=\frac{1}{2\pi \times fc\times Rp}=\frac{1}{2\pi \times 20\times 70.9\times 10^3}\approx 0.11\mu \text{F}$

8. Calculate Capacitor C2 :
   $C2=\frac{1}{2\pi \times fc\times ZL}=\frac{1}{2\pi \times 20\times 10\times 10^3}\approx 0.796\mu \text{F}$

Output Results :

• $Ve=7.5\text{V}$
• $Re=7.5\text{kΩ}$
• $R1=128.3\text{kΩ}$
• $R2=150\text{kΩ}$
• $C1=0.11\mu \text{F}$
• $C2=0.8\mu \text{F}$

Practical Example

Imagine you're designing a microphone preamplifier for an electret microphone. The microphone outputs a weak audio signal (20 Hz to 20 kHz), which needs buffering before amplification. Using this calculator:

• You input the supply voltage, quiescent current, and load impedance.
• The calculator determines the resistor and capacitor values needed to achieve a stable, low-distortion output.
• With the calculated values, you can confidently build the circuit, knowing it will perform reliably across the entire audio frequency range.

This tool ensures that your emitter follower circuit is optimized for both performance and efficiency , saving time and effort in the design process.