The HM4558S, introduced by HeroMicro, is a classic dual, high-gain, internally frequency-compensated general-purpose operational amplifier. Renowned for its wide supply voltage range, low power consumption, high reliability, and the key feature of requiring no external compensation, it has found widespread use in industrial control, consumer electronics, and various analog signal processing circuits. This chip serves as a compatible replacement for many classic op-amps (such as the LM4558, UA4558).
1. Key Features Overview
Based on the datasheet provided by HeroMicro (HM4558S.pdf), key features include:
Dual Channel Integration: Contains two completely independent, high-performance op-amps in a single package.
Wide Supply Voltage Range:
Single Supply: +3V to +36V
Dual Supply: ±1.5V to ±18V
Internal Frequency Compensation: No external compensation capacitor is required for stable operation, greatly simplifying circuit design.
Excellent DC Performance:
Input Offset Voltage (VIO): Typical 1mV
Common-Mode Rejection Ratio (CMRR): Typical 90dB
Large-Signal Voltage Gain (AVD): Typical 300 V/mV (106dB)
Good AC Performance:
Unity-Gain Bandwidth (GBW): 3MHz (Typical)
Slew Rate (SR): 0.8 V/μs (Typical)
Low Noise & Low Power:
Equivalent Input Noise: 8 nV/√Hz (@1kHz)
Quiescent Current: Typical 1.4mA per channel (Total ~2.8mA)
Package Options: SOP-8, DIP-8, SIP-8, catering to different assembly requirements.
2. Pin Configuration (SOP-8/DIP-8)
| Pin | Symbol | Function |
|---|---|---|
| 1 | 1OUT | Output of Channel 1 |
| 2 | 1IN- | Inverting Input of Channel 1 |
| 3 | 1IN+ | Non-inverting Input of Channel 1 |
| 4 | VCC- | Negative Supply (Ground for single supply) |
| 5 | 2IN+ | Non-inverting Input of Channel 2 |
| 6 | 2IN- | Inverting Input of Channel 2 |
| 7 | 2OUT | Output of Channel 2 |
| 8 | VCC+ | Positive Supply |
3. Critical Design Guidelines
(1) Power Supply Connection
Single Supply Application: The most common usage. Connect VCC+ (Pin 8) to the positive rail (e.g., +5V, +12V) and VCC- (Pin 4) to Ground (GND).
Dual Supply Application: Used for handling AC signals or when the output needs to swing below ground. For example, VCC+ to +15V and VCC- to -15V.
Power Supply Decoupling: It is highly recommended to place a 0.1μF ceramic capacitor close between the VCC+ and VCC- pins to filter high-frequency noise and ensure stability.
(2) Basic Application CircuitsThanks to its internal compensation, the HM4558S can be directly used in various standard op-amp configurations:
Inverting/Non-inverting Amplifiers: Set gain with external resistors. The datasheet (page 4) provides the standard non-inverting formula VOUT = (1 + RF/RG) * VIN.
Voltage Follower (Buffer): Connect the output directly back to the inverting input, with the signal source at the non-inverting input. This offers high input impedance and low output impedance, commonly used for isolation.
Summing/Subtracting Amplifiers: Built using the virtual short/open principles of op-amps.
Active Filters: Can be used to construct 1st or 2nd order low-pass or high-pass filters.
(3) Input & Output Limitations
Common-Mode Input Voltage Range (VICR): With ±15V supplies, the typical range is ±14V. Input signals cannot get too close to the supply rails.
Maximum Output Voltage Swing (VOM): With ±15V supplies and a 10kΩ load, the typical swing is ±14V. The output cannot reach the supply rails and will have a 1-2V dropout. The swing decreases further under heavy loads (e.g., RL=2kΩ).
(4) Channel-to-Channel Crosstalk
The datasheet states a typical crosstalk attenuation of 85dB (open-loop) or 105dB (AV=100). This indicates very little interaction between the two channels, which is negligible in most applications.
(5) Important Notes
Latch-up Immunity: The datasheet explicitly states the device is "latch-up free", enhancing its reliability in harsh environments.
ESD Handling: Although not explicitly rated in the document, as a Bipolar process device, standard ESD precautions should be followed during handling.
Application Restrictions: Per the disclaimer at the end of the datasheet, this product is not intended for life-support, rescue, or safety-critical equipment where failure could cause personal injury or significant property damage.
4. Typical Applications
Audio pre-amplifiers and active filters
Sensor signal conditioning circuits (e.g., strain gauges, thermocouples)
PID controllers in industrial process control
Buffer and gain stages in data acquisition systems
Function generators and simple comparator circuits (though not a dedicated comparator)
5. Summary
HeroMicro's HM4558S is a mature, reliable, and versatile dual general-purpose operational amplifier. Its features of internal compensation, wide voltage range, and ease of use make it an ideal choice for a vast array of analog circuit designs, from simple amplification to complex signal processing. By following basic guidelines for power supply decoupling and PCB layout, engineers can quickly and efficiently integrate it into their systems.
