Gain-Bandwidth Product (GBP)
The Gain-Bandwidth Product (GBP) of an operational amplifier (op-amp) is a constant value that relates:
- Amplifier Gain
- Operating Bandwidth
It tells us:
Mathematical Definition
or
Where:
- Av = Voltage gain
- BW = Bandwidth
- fT = Unity-gain frequency
Important Concept
Therefore:
- High Gain → Small Bandwidth
- Low Gain → Large Bandwidth
The product remains approximately constant.
Example
Suppose an op-amp has:
Case 1: Gain = 10
The amplifier works properly up to 100 kHz.
Case 2: Gain = 100
Increasing gain reduces bandwidth.
Why GBP Matters
GBP helps determine:
- Maximum usable frequency
- Stable amplifier operation
- Speed of op-amp circuits
Applications of Gain-Bandwidth Product
1. Designing Amplifiers
Used to select op-amps for required gain and frequency range.
Example:
- Required Gain = 50
- Signal Frequency = 20 kHz
Required GBP:
2. Audio Amplifiers
Audio systems require moderate gain and wide bandwidth. GBP ensures accurate sound amplification.
3. Communication Systems
Used in:
- RF Amplifiers
- Filters
- Signal Conditioning Circuits
4. Active Filters
Filters require sufficient GBP to maintain correct response. Low GBP may cause:
- Distortion
- Incorrect cutoff frequency
5. High-Speed Signal Processing
Applications include:
- ADC Drivers
- Video Amplifiers
- Instrumentation Amplifiers
Relation with Closed-Loop Gain
| Closed-Loop Gain | Bandwidth |
|---|---|
| 1 | 1 MHz |
| 10 | 100 kHz |
| 100 | 10 kHz |
Summary
| Parameter | Meaning |
|---|---|
| Gain-Bandwidth Product | Constant relation between gain and bandwidth |
| Formula | GBP = Gain × BW |
| High Gain Effect | Reduces bandwidth |
| High Bandwidth Effect | Reduces gain |
This limitation is described by the Gain-Bandwidth Product (GBP).