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  The Differential Amplifier A differential amplifier is an operational amplifier circuit that amplifies the difference between two input voltages . Instead of measuring a signal relative to ground, it measures how much one signal differs from another . This makes differential amplifiers incredibly useful for: Rejecting noise Comparing signals Sensor interfaces Audio and measurement circuits In simple mathematical terms: Output = (Input 1 – Input 2) × Gain In the real world, signals are often noisy. Long wires, motors, power supplies, and digital circuits can all introduce interference. A differential amplifier helps by: Amplifying only the difference between inputs Rejecting signals that appear equally on both inputs (called common-mode signals ) The Basic Differential Amplifier Circuit Differential Amplifier Circuit A classic differential amplifier uses four resistors and one op-amp. For proper operation: Resistor ratios must match This ensures accurate subtract...

The Summing Amplifier In this part of the op-amp series, we’re going to build and test summing amplifiers . A summing amplifier combines multiple input signals into one output , making it one of the most useful and flexible op-amp building blocks. In this post we will: Build two types of summing amplifier Measure real voltages on the bench Match the math directly to what we measure Highlight practical limitations with single-supply op-amps What Is a Summing Amplifier? A summing amplifier is an op-amp circuit that adds multiple input signals together and produces a single output voltage. Key idea (very important): 👉 Summing amplifiers add currents , not voltages. 👉 The op-amp output converts the summed current back into a voltage. Each input voltage is converted into a current by a resistor. Those currents are summed at the op-amp input and converted back into a voltage at the output. There are two basic types of summing amplifiers: - Inverting Non-Inverting Type 1 — Inverti...