The LM1458 dual operational amplifier is a general-purpose op amp IC designed for basic analog signal processing. It contains two independent operational amplifiers in one package, so it can handle two amplifier stages or two different signal functions in the same circuit. Because it supports typical dual-supply operation such as ±9 V, ±12 V, or ±15 V, it is still practical for older analog circuits, educational projects, and low-frequency designs. This article explains the LM1458’s specifications, pinout, internal structure, alternatives, circuit applications, and more.

Catalog

Features and Specifications of LM1458

LM1458 Pinout Details

Internal Structure and Working Principle

The MC1458

Common LM1458 Circuit Applications

LM1458 Function Generator Circuit

The LM1458 used as a basic function generator. It produces three common waveform outputs: square wave, triangle wave, and sine wave. The circuit uses the two internal op amps of the LM1458 together with resistors and capacitors to shape the signal step by step. The supply uses both +9 V and -9 V, which allows the output waveform to swing above and below ground.

In this circuit, one op amp section works as an oscillator or switching stage to create the square wave. The square wave then passes through an integrating section, where the capacitor charges and discharges in a controlled way. This changes the sharp square wave into a smoother triangle wave. After that, the resistor-capacitor network further shapes the triangle wave into a more rounded sine wave. This shows how the LM1458 can be used not only for amplification but also for waveform generation and signal shaping.

This application is useful for testing audio circuits, filters, amplifiers, and basic analog systems. However, because the LM1458 has a limited slew rate and bandwidth, this type of circuit is better for low-frequency signals. It is not suitable for high-frequency waveform generation where a faster op amp or dedicated function generator IC would perform better.

LM1458 Relay Control Circuit

The LM1458 used in a sensor-based relay control circuit. The coil marked L1 acts as the sensing element. The LM1458 compares the voltage from the sensing coil with a reference voltage set by the resistors. When the input signal reaches the required level, the output of the LM1458 changes state and drives the transistor.

The transistor, shown as 2N3053, works as a relay driver because the LM1458 cannot directly supply enough current to energize the relay coil. When the op amp output turns the transistor on, current flows through the relay coil and the relay switches. The diode across the relay coil protects the transistor and the IC from voltage spikes generated when the relay turns off.

This circuit shows how the LM1458 can be used as a signal detector and control amplifier. It reads a small input signal, compares it with a set threshold, and controls a larger load through a transistor. In real use, this type of circuit can be adapted for magnetic sensing, object detection, alarm systems, or automatic switching. The important point is that the LM1458 handles the signal decision, while the transistor handles the higher current required by the relay.

LM1458 Audio Amplifier Circuit

The LM1458 used in a small audio amplifier circuit. The input signal comes from an 8-ohm speaker or microphone-like source and is coupled into the LM1458 through a capacitor and resistor network. The LM1458 amplifies the small audio signal and sends it to the transistor stage.

The transistor 2N3053 is used as the output driver because an LM1458 alone cannot drive an 8-ohm speaker with enough current. The op amp provides voltage gain, while the transistor provides current gain. This combination allows the circuit to drive the output speaker more effectively than the op amp alone. The capacitors in the circuit help block DC, stabilize the bias point, and allow the audio signal to pass.

This circuit is useful for simple audio experiments, small signal amplification, intercom circuits, and learning how op amps and transistors work together. However, it is not a high-quality audio amplifier. The LM1458 has limited slew rate, noise performance, and output drive compared with modern audio op amps. For better sound quality, parts like NE5532, LM833, or TL072 are usually better choices.

When Should You Use or Not Use LM1458

Use LM1458 When

You can use the LM1458 when your circuit needs a simple and low-cost dual operational amplifier for basic analog work. It is suitable for low-frequency applications such as signal amplification, active filters, summing amplifiers, integrators, voltage followers, and simple waveform-shaping circuits. Since it has two op amps in one package, it is useful when you need two amplifier stages while saving board space.

The LM1458 is also a good choice for learning, testing, and repairing older circuits. Many classic analog circuits were designed around dual-supply op amps, so the LM1458 can still work well in systems using supplies such as ±9 V, ±12 V, or ±15 V. It is practical when the circuit does not require very high speed, very low noise, rail-to-rail output, or precision accuracy.

You may also use LM1458 when cost and availability are more important than advanced performance. For simple control circuits, audio experiments, general signal conditioning, and educational projects, the LM1458 can still perform properly if the supply voltage, input range, load current, and frequency limits are respected.

Do Not Use LM1458 When

Do not use the LM1458 when your circuit requires low-voltage operation, especially with modern 3.3 V or 5 V microcontroller systems. The LM1458 is not a rail-to-rail op amp, so its input and output voltage range cannot reach the supply rails. This can cause clipped, weak, or incorrect output signals in low-voltage single-supply circuits.

You should also avoid the LM1458 in high-speed or high-frequency applications. Its typical slew rate is only about 0.5 V/µs, so it is not ideal for fast signal processing, high-frequency waveform generation, fast ADC driving, or switching applications that need quick response. A faster op amp is a better choice for these designs.

The LM1458 is also not the best option for precision sensor circuits, battery-powered devices, and high-quality audio designs. Its input offset voltage, input bias current, noise performance, and power consumption are not as good as many modern op amps. For precision measurement, low-power systems, low-noise audio, or high-input-impedance sensors, newer alternatives such as MCP6002, TL072, NE5532, LM358, or precision CMOS op amps are usually more suitable.

Real World Applications

• Active filters

• Audio preamplifiers

• Signal conditioning circuits

• Voltage followers

• Inverting amplifiers

• Non-inverting amplifiers

• Summing amplifiers

• Integrator circuits

• Differential amplifiers, etc.

Mechanical Dimensions

Conclusion

The LM1458 remains a useful dual operational amplifier for simple and low-frequency analog circuits. Its main strengths are its dual-op-amp structure, internal frequency compensation, short-circuit protection, wide supply voltage support, and easy use in basic amplifier and filter designs. It can be a good choice for learning electronics, repairing older circuits, building simple signal-conditioning stages, and creating basic function generator, relay control, or audio amplifier circuits. However, the LM1458 also has clear limits. Its slew rate, input offset, input bias current, output drive, and non-rail-to-rail behavior make it less suitable for modern 3.3 V or 5 V systems, precision sensors, battery-powered devices, high-speed signals, and high-quality audio applications. For these needs, newer op amps such as LM358, TL072, NE5532, MCP6002, or other modern CMOS and audio op amps may be better options.