The LM339 is a quad-voltage comparator, which means it contains four separate comparators. The LM324 is a quad operational amplifier (op-amp) with four amplifiers. While it is not explicitly designed as a comparator, it can still be used for basic comparator applications due to its high gain and similar functionality.
LM339 IC vs LM324 IC
Pin Configuration
LM339: The LM339 typically comes in a 14-pin. Each comparator has two input pins (inverting and non-inverting), one output pin, and a ground pin.
LM324: Each op-amp in the LM324 contains two input pins (one inverting and one non-inverting), one output pin, and a ground pin. It also comes in a 14-pin package.
Fig: Pin Diagram of LM339 IC.
Fig: Pin Diagram of LM324 IC.
| LM339 | LM324 | ||
| Number of channels | 4 | Number of channels | 4 |
| Iq per channel (typ) (mA) | 0.2 | 4 Iq per channel (typ) (mA) | 0.175 |
| Input bias current (±) (nA) | 50 | Input bias current (pA) | 250000 |
| Supply Voltage (max) (V) | 30 | Supply Voltage max) (V) | 32 |
| Supply Voltage (min) (V) 2 | 2 | Supply Voltage (min) (V) 3 | 3 |
| Rail-to-rail | Out | Rail-to-rail | In to V- |
| Offset voltage at 25°C (mV) | 5 | Offset voltage at 25°C (mV) | 7 |
| Slew rate (typ) (V/µs) | Not Specified | Slew rate (typ) (V/µs) | 0.5 |
| Operating temperature range (°C) | 0 to 70 | Operating temperature range (°C) | 0 to 70 |
Number of Comparators
LM339: It contains four independent voltage comparators in a single package.
LM324: It consists of four separate operational amplifiers in a single package.
Input Offset Voltage and Common Mode Rejection Ratio (CMRR)
LM339: Compared to op-amps, voltage comparators like the LM339 have a lower input offset voltage and a higher common mode rejection ratio (CMRR). They are therefore more suited for applications requiring precision voltage comparison, where it is necessary to measure even the smallest voltage variations accurately.
LM324: Compared to specialized comparators, op-amps like the LM324 may have a marginally greater input offset voltage and a lower CMRR. They may not be as accurate as voltage comparators in some high-precision workloads, but they still offer acceptable performance for most op-amp applications.
Schmitt Trigger Action
LM339: The LM339 often includes hysteresis also known as Schmitt trigger action, which prevents output oscillation when the input voltages are near the threshold point. This capability is beneficial when dealing with input signals that slowly change or in noisy situations.
LM324: LM324 typically lacks built-in Schmitt Trigger Action. As a result, they could require extra hardware or circuitry to implement hysteresis for uses where noise immunity is crucial.
Functionalities
LM339: The LM339 is specifically designed as a voltage comparator, optimized for comparing two input voltages and producing a digital output based on their relationship. The LM339 features an open-drain output, which allows direct interfacing with other digital devices for various logic implementations, making it suitable for applications requiring digital switching.
LM324: The LM324 is primarily an operational amplifier (op-amp). Op-amps are designed for amplifying and processing analog signals, providing high gain and linearity, making them suitable for various signal conditioning and mathematical operations, making them a popular choice for a wide range of applications.
While not a dedicated comparator, the LM324 can be used for basic comparator applications due to its open-loop configuration and high gain.
Cost-Effectiveness
LM339: Cost-Generally more expensive than LM324, as specialized voltage comparators are less common and may have higher unit costs.
LM324: More cost-effective due to its widespread use and larger production volumes, leading to lower unit costs.
Frequently Asked Questions (FAQs)
1. What comparator is equivalent to LM339?
Answer: The equivalents of LM339 are LM311, LM2901, LM239, LM139, LM397 and LM324.
2. How does the open-drain output of the LM339 differ from the standard op-amp outputs of the LM324?
Answer: The open-drain output of the LM339 can only pull the output voltage to the ground, requiring an external pull-up resistor for high-level voltage. In contrast, the standard op-amp outputs of the LM324 can actively drive the high and low output voltage without additional circuitry.
To Conclude
The LM339 and LM324 are different integrated circuits with distinct functionalities. The LM339 is a dedicated voltage comparator with an open-drain output, ideal for digital switching applications, while the LM324 is a quad operational amplifier primarily used for analog signal processing tasks. Understanding these differences is important as it helps to choose the appropriate IC for specific applications, ensuring optimal performance and efficiency, and cost-effectiveness in electronic designs.
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