The LM301A is a single general-purpose operational amplifier designed for analog signal amplification, monitoring, control, and waveform-generation applications. Its main difference from many modern op-amps is its external frequency compensation, which allows the you to adjust the balance between stability, bandwidth, and response speed. This flexibility can be useful, but the wrong compensation network may cause oscillation, ringing, or slow operation. The LM301A also includes offset adjustment, a Class AB output stage, short-circuit protection, and operation from dual power supplies.

Catalog

How Does the LM301A Work?

Internal transistor structure of the <a href="https://www.y-ic.com/pdf/TI/LM301A.html" target="_blank" "="" style="cursor: pointer; color: rgb(0, 0, 238); font-weight: bold;">LM301A operational amplifier. The signal enters through the inverting input, marked IN(−), and the non-inverting input, marked IN(+). Transistors Q1 to Q4 form the main differential input stage. This stage compares the two input voltages and produces an internal signal based on their difference. If the non-inverting input is more positive than the inverting input, the output moves positive. If the inverting input is more positive, the output moves negative.

The transistors in the middle of the diagram provide most of the LM301A’s voltage gain. They amplify the small signal produced by the input stage before passing it to the output section. The surrounding resistors and current-control transistors establish stable operating currents so that the amplifier can work consistently as the input signal and supply voltage change.

The compensation connections allow an external capacitor to control the amplifier’s frequency response. Unlike an internally compensated op-amp, the LM301A requires a suitable external compensation network for stable operation in many circuits. Changing the compensation value affects bandwidth, slew rate, settling time, and stability. A larger compensation capacitor generally improves stability but slows the amplifier, while a smaller value can increase speed but may cause ringing or oscillation.

The offset-null connections allow the user to correct small DC errors in the input stage. An external adjustment circuit can balance the internal transistors and reduce the output voltage that appears when both inputs should be at the same level. This adjustment is especially useful in DC measurement and signal-conditioning circuits where a small offset could affect accuracy.

On the right side, Q11 to Q16 form the output-driver section. This Class AB stage supplies current to the load and allows the output voltage to move in both positive and negative directions. It also provides better linearity than a basic single-ended output stage. However, the LM301A is not rail-to-rail, so its input and output voltages must remain within the limits given in the datasheet. Negative feedback around the complete op-amp then sets the required circuit gain and makes the output follow the intended relationship between the two inputs.

LM301A Technical Specifications

LM301A Features and Advantages

• External frequency compensation: Allows the compensation capacitor to be selected for the required stability, bandwidth, and response speed.

• High slew rate with optimized compensation: Can achieve up to 10 V/µs in a properly compensated summing-amplifier circuit.

• Class AB output stage: Provides good output linearity while allowing the output voltage to move in positive and negative directions.

• Low input bias current: Reduces measurement errors when the LM301A is connected to relatively high-resistance signal sources.

• Low input offset current: Helps reduce DC errors caused by differences between the two input bias currents.

• Output short-circuit protection: Protects the output stage against continuous short circuits, subject to safe temperature and power limits.

• Latch-free operation: The amplifier recovers normally when the input temporarily exceeds its common-mode range.

• Offset-null capability: External components can be used to reduce the input offset voltage in accuracy-sensitive circuits.

• Wide input-voltage range: Supports relatively large bipolar signals when operated from a suitable dual power supply.

• Adjustable stability and speed: The external compensation network can be optimized for stable low-frequency operation or faster response at higher closed-loop gains.

LM301A Pinout and CAD Models

LM301A Pinout

LM301A CAD Models

LM301A Frequency Compensation

The LM301A uses external frequency compensation to control its high-frequency response and maintain stable operation. In the diagram, the 30 pF capacitor forms the standard compensation network. It limits the amplifier’s high-frequency open-loop gain before excessive phase shift can turn negative feedback into positive feedback. This helps prevent unwanted oscillation, ringing, and overshoot, especially when the LM301A operates at a low closed-loop gain.

The 30 pF capacitor provides standard single-pole compensation and is normally suitable when stable operation is more important than maximum speed. Increasing the compensation capacitance generally improves the stability margin but reduces bandwidth and slows the output response. Using a smaller capacitor can increase bandwidth and slew rate, but the circuit may become more sensitive to PCB layout, feedback-network values, and capacitive loading. Therefore, the compensation network should not be changed without checking the output with an oscilloscope.

The diagram also includes an offset-balancing network made from the 10 MΩ and 5.1 MΩ resistors and a 20 kΩ adjustable resistor. This network is separate from the main feedback path. It allows a small correction to the internal input-stage balance, reducing the output offset that may appear when both inputs are at the same voltage. The adjustment is useful in DC and measurement circuits but can be omitted when a small offset is acceptable.

The VCC and VEE terminals supply the positive and negative operating voltages, while the inverting and non-inverting terminals receive the input signals. The compensation capacitor does not set the circuit’s closed-loop gain; external feedback components connected around the input and output perform that function. Supply-bypass capacitors should also be placed close to the IC, but they do not replace the required frequency-compensation capacitor.

LM301A Application Circuits

LM301A Inverting Amplifier

This circuit uses the LM301A as an inverting amplifier. The input signal passes through the 500 Ω resistor R1, while the 10 kΩ resistor R2 provides negative feedback. The voltage gain is -R2/R1, giving a gain of −20. Therefore, the output is amplified twenty times and has the opposite polarity from the input.

LM301A Current Monitor

The 0.1 Ω resistor R1 produces a small voltage proportional to the load current. The LM301A detects this voltage and controls the 2N3684 transistor. R2 and R3 convert the measured current into a monitor output of approximately 5 V per ampere using the values shown.

Low-Frequency Square-Wave Generator

This circuit uses the LM301A as a relaxation oscillator. C1 charges and discharges through R1, while R2 and R3 provide the switching thresholds needed to reverse the output repeatedly. R4 limits current, and the two 6.2 V Zener diodes clamp the second output to a controlled voltage. The circuit provides both a low-impedance output and a voltage-clamped output.

Integrator with Bias-Current Compensation

This circuit uses the LM301A to produce an output proportional to the accumulated input signal over time. R1 and the feedback capacitor set the integration rate. The resistor and diode network provides bias-current compensation, helping reduce output drift caused by the LM301A’s input bias current. The 30 pF capacitor provides the required frequency compensation for stable operation.

Common LM301A Applications

• Industrial automation equipment

• Laboratory measuring instruments

• Analog control systems

• Regulated power supplies

• Battery chargers

• Motor-control equipment

• Temperature-monitoring equipment

• Pressure-monitoring systems, etc.

LM301A vs Equivalents and Replacements

Common LM301A Circuit Problems

• Output oscillation: Usually caused by missing or incorrect frequency compensation.

• Signal clipping: Occurs when the input or output exceeds its allowed voltage range.

• Output stuck at a rail: Often caused by incorrect feedback, reversed inputs, or saturation.

• Incorrect gain: Results from wrong resistor values or feedback connections.

• High DC offset: Caused by input offset, bias current, or incorrect offset adjustment.

• Slow response: An oversized compensation capacitor reduces speed and bandwidth.

• Excessive noise: May result from poor grounding, missing bypass capacitors, or long signal paths.

• Load-driving problems: Heavy or capacitive loads can reduce output swing or cause instability.

• Incorrect replacement: Substitute op-amps may use different compensation and offset-null pins.

LM301A Mechanical Package

Manufacturer

ONSEMI manufactures semiconductor products through a global network that supports wafer fabrication, IC assembly, packaging, testing, and quality control. The LM301A is a monolithic bipolar operational amplifier produced on a silicon chip and tested for key parameters such as offset voltage, input current, voltage gain, supply current, and temperature performance. The current onsemi datasheet lists the LM301ADR2G in a Pb-free SOIC-8 tape-and-reel package, while older PDIP-8 versions were discontinued in July 2025. onsemi does not publicly identify the exact manufacturing site for each LM301A production lot.