LM12 is a power operational amplifier integrated circuit (IC) developed by National Semiconductor (now owned by Texas Instruments). It is designed for use in high-power audio amplifiers, servo amplifiers, and other high-current applications.
Here are the electrical specifications and technical datasheet of the LM12:
- Supply voltage: +/-10V to +/-40V
- Output current: 5A to 10A.
- Output voltage swing: +/-30V
- Input offset voltage: 2mV
- Input bias current: 300nA
- Input voltage range: +/-10V
- Slew rate: 20V/µs
- Gain bandwidth product: 5MHz
- The LM12 is a monolithic power operational amplifier that consists of a high-voltage, NPN output transistor, and a PNP input transistor.
- It is internally compensated for stable operation and can be configured for unity-gain operation by connecting the feedback resistor between the output and the inverting input.
- The LM12 can drive loads up to 50 ohms without external compensation and provides high output current, high slew rate, and wide bandwidth.
- The IC also features thermal shutdown protection, which shuts down the output stage when the chip temperature exceeds the safe operating range.
- The LM12 is available in a 8-pin TO-3 metal can package and operates over a temperature range of -55°C to +125°C.
Overall, the LM12 is a high-performance power amplifier IC that can deliver high output current and voltage swing with low distortion, making it suitable for demanding applications that require high power and high fidelity.
We now come to the last power amplifier that we wanted to present to you. It is one of the most powerful since it allows for an output voltage ranging from +/- 25 V with a current easily reaching +/- 10 A.
It is capable of providing a sinusoidal signal with a power of 80 W into a load of 4 Ohm, with a distortion of 0.01%.
The IC LM12 pinout configuration and a typical application of a high-power audio frequency amplifier are given in Figure below.
Main Features of LM12 IC
Its characteristics are as follows:
- Internal protection
- Internal temperature limitation
- Protection against higher than normal voltages
- Several LM12s can be connected in parallel to increase output power, as shown in the diagram in Figure below.
The internal circuitry of LM12 IC is given in Figure below.
Its main applications are power supply design, high voltage regulators, high-quality audio frequency amplifiers, and servo motor control.
Operational amplifiers are usually powered by symmetrical voltages.
Servo Motor Controller
However, it is very convenient to be able to power LM12 IC with a single voltage supply, as shown in the diagram below, which shows the control of a servo motor.
One of the inputs can be grounded, with the other controlling the direction of rotation. It is also possible to apply a positive reference voltage to one of the inputs and vary the control signal around this value.
Servo Motor Control with Tachometer
The last application of the IC LM12 is shown in Figure below. It is a servo motor control using a tachometer coupled to the motor shaft. The speed is variable depending on the input signal value.