A differential amplifier bridge amplifier is a specialized electronic circuit that combines the functionality of a differential amplifier and a bridge amplifier. It is widely used in applications that require high precision, noise immunity, and the ability to amplify small voltage differences, such as strain gauge measurements and data acquisition systems.
Technical Specifications
Gain
- The gain of a differential amplifier bridge amplifier is typically high, ranging from 50 to 100. This high gain allows for the effective amplification of small voltage differences between the input signals.
Input Voltage Range
- The input voltage range of a differential amplifier bridge amplifier depends on the specific operational amplifier (op-amp) used in the circuit. For example, the LM358 op-amp can handle input voltages up to 32V, while the TLV2772A op-amp can handle input voltages up to 36V.
Common-Mode Rejection Ratio (CMRR)
- The CMRR of a differential amplifier bridge amplifier is typically high, often exceeding 80 dB. This high CMRR ensures that the amplifier effectively rejects common-mode noise and only amplifies the desired differential signal.
Noise Immunity
- Differential amplifier bridge amplifiers are highly resistant to external noise sources due to their differential signaling architecture. This makes them suitable for use in noisy environments, where they can maintain high accuracy and reliability.
Output Voltage Swing
- The output voltage swing of a differential amplifier bridge amplifier can be quite high, often up to 90% of the supply voltage. This large output voltage range allows the amplifier to be used in a variety of applications.
Physics and Theoretical Explanation
The operation of a differential amplifier bridge amplifier is based on the principles of differential signaling and amplification. The amplifier takes two input signals, V1 and V2, and amplifies their difference, Vdm = V1 - V2. This is achieved through a combination of resistors and op-amps that create a differential gain stage.
The output voltage of the amplifier can be expressed as:
Vout = KVdm + Vref
where K is the gain of the amplifier and Vref is the reference voltage.
Examples and Numerical Problems
Strain Gauge Measurement
Consider a strain gauge connected to a Wheatstone bridge, which is then connected to a differential amplifier bridge amplifier. If the strain gauge resistance changes from 350 Ohms to 351 Ohms, the output voltage of the bridge changes from -5.365 mV to -5.365 mV + 134 mV = 128.635 mV.
Differential Gain Calculation
Given a differential amplifier bridge amplifier with resistors R1 = R2 = 1 kΩ and R3 = R4 = 50 kΩ, calculate the differential gain K.
K = R3/R1 = 50 kΩ/1 kΩ = 50
Figures and Data Points
Circuit Diagram
A typical differential amplifier bridge amplifier circuit consists of a Wheatstone bridge connected to a differential amplifier stage, which is then followed by additional gain stages.
Output Voltage vs. Input Voltage
The output voltage of the amplifier increases linearly with the differential input voltage, with a slope determined by the gain of the amplifier.
Measurements and Applications
Strain Gauge Measurements
Differential amplifier bridge amplifiers are commonly used in strain gauge measurements to amplify the small voltage changes produced by the strain gauge. This allows for accurate monitoring and analysis of mechanical deformation in various structures and materials.
Data Acquisition Systems
These amplifiers are also used in data acquisition systems to amplify and condition signals from various sensors, ensuring high accuracy and noise immunity. This is particularly important in applications where the input signals are weak or susceptible to interference, such as in industrial automation, biomedical instrumentation, and environmental monitoring.
References
- Electronics Tutorials. (n.d.). Differential Amplifier – The Voltage Subtractor. Retrieved from https://www.electronics-tutorials.ws/opamp/opamp_5.html
- Texas Instruments. (2002). Fully-Differential Amplifiers (Rev. E). Retrieved from https://www.ti.com/lit/an/sloa054e/sloa054e.pdf
- Embedded Related. (2014). How to Analyze a Differential Amplifier. Retrieved from https://www.embeddedrelated.com/showarticle/557.php
- Curious Scientist. (2023). Strain gauge, Wheatstone bridge, differential amplifier – Educational device. Retrieved from https://curiousscientist.tech/blog/strain-gauge-wheatstone-bridge-differential-amplifier-educational-device
- NI Community. (2014). op amp differential amplifier measurements. Retrieved from https://forums.ni.com/t5/LabVIEW/op-amp-differential-amplifier-measurements/td-p/2861666
Hi, I am Amrit Shaw. I have done Master in Electronics.
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