NE570 - Dual Gain Control Circuit

Overview

The NE570 is a versatile, low-cost dual gain control circuit designed for dynamic range compression and expansion applications. Each channel of this IC can be independently configured as either a compressor or expandor, making it highly flexible for various audio processing needs. The device features a full-wave rectifier for signal detection, temperature compensation, and a wide dynamic range exceeding 110 dB. With its ability to operate from a 6V DC supply, the NE570 is suitable for both portable and fixed audio equipment.

This IC is particularly valuable in systems requiring dynamic signal processing, such as noise reduction, level control, and voltage-controlled amplification. The NE570's architecture allows for external component adjustment of system levels and distortion trimming, providing designers with significant control over the audio processing characteristics.

Key Features

• Complete compressor and expandor functionality in a single IC package
• Temperature-compensated design for stable operation across varying conditions
• Exceptional dynamic range exceeding 110 dB
• Low voltage operation down to 6V DC
• Adjustable system levels through external components
• Distortion trimming capability for optimized audio quality
• Dual-channel architecture for independent processing
• Integrated full-wave rectifier for accurate signal detection

Applications

The NE570 finds use in a wide range of audio processing and telecommunications applications:

• Cellular radio systems: For dynamic range control and noise management
• Telephone trunk compandors: Implementing companding algorithms for improved signal transmission
• High-level limiters: Protecting equipment from signal overloads
• Low-level expandors (noise gates): Reducing noise during silent passages
• Dynamic noise reduction systems: Improving signal-to-noise ratios
• Voltage-controlled amplifiers: For gain modulation applications
• Dynamic filters: Creating frequency-dependent gain control systems

Electrical Characteristics

Absolute Maximum Ratings

AC Electrical Characteristics (V_CC = +6V, T_amb = 25°C)

Package Information

Pin Configuration

The NE570 is available in a 16-pin SO16 (Small Outline) package with the following pinout:

1. RECT_CAP_1
2. RECT_IN_1
3. ∆G_CELL_IN_1
4. GND
5. RECT_CAP_2
6. RECT_IN_2
7. V_CC
8. RES_R3_1
9. OUTPUT_1
10. THD_TRIM_1
11. RES_R3_2
12. OUTPUT_2
13. THD_TRIM_2
14. INV_IN_1
15. INV_IN_2
16. ∆G_CELL_IN_2

Ordering Information

Functional Description

The NE570 consists of two independent channels, each containing several key functional blocks:

• Rectifier: Full-wave design for accurate signal level detection
• Variable Gain Cell: Provides the compression/expansion function
• Inverter: For signal phase management
• THD Trim: Allows for distortion adjustment

The device operates by comparing the input signal level (detected by the rectifier) to a reference voltage and adjusting the gain accordingly. The time constants for attack and release can be set using external capacitors connected to the RECT_CAP pins.

Design Considerations

When implementing the NE570 in a circuit design, several factors should be considered:

• Power supply decoupling is essential for optimal performance
• The THD_TRIM pins allow for fine-tuning of harmonic distortion
• External resistors at the R3 pins set the system's gain characteristics
• The rectifier capacitors determine the time constants for dynamic response
• Proper grounding is crucial to maintain channel separation

The NE570's flexibility makes it suitable for both professional audio equipment and consumer electronics, provided the design accounts for the specific application requirements regarding dynamic range, distortion, and frequency response.