• Features/Applications/Description
  • Key Specifications
  • Packaging/Pricing/Samples
  • Design Notes
  • Additional Resource


• High Performance Blackmer® VCA, RMS-Level Detector, and three Opamps in one package
• Wide Dynamic Range:
> 105 dB
• Low THD: < 0.09 %
• Low Power: 7 mA typ.
• Surface-Mount Package
• 5 VDC Operation


• Wireless microphone systems
• Wireless in-ear monitors
• Compressors
• Limiters
• Gates
• De-essers
• Duckers

Datasheet Download
4311 Datasheet (427 kB)
Low-voltage Low-power Dynamics Processor IC


The THAT 4311 Low-voltage Low-power Dynamics Processor combines in a single IC all the active circuitry needed to construct a wide range of dynamics processors that operate off of as little as 0 – 5 Volts. The 4311 includes a high performance, Blackmer® voltage controlled amplifier, a log responding RMS-level sensor and three opamps, one of which is dedicated to the VCA, while the other two may be used for the signal path or control voltage processing.

Key Specifications (see 4311 datasheet for complete specifications)

 Parameter Conditions Typical Units
 Power supply voltage +5 to +15 V
 Supply current 7V 7 mA


 Dynamic Range 105 dB
 Gain Range < -100 to > +30 dB
 Total Harmonic Distortion 0.09 %
 Control Constant
(both positive & negative-
sense control available)
± 6.1 mV/dB
 Output Noise 0 dB gain dBV

 RMS Detector

 Averaging Method Root Mean Squared (RMS)
 Output Scaling +6.1 mV/dB
 Dynamic Range > 80 dB
 Bandwidth > 20 kHz
 Crest Factor 1 dB reading error 10
 Input Offset Voltage ± 0.5 mV
 Gain-Bandwidth Product 5 MHz
 Slew Rate 2 V/µs
 Input Voltage Noise OA1
OA2 & 3




Order Number


Min Order



20 Pin SO





20 Pin SO
Tape & Reel


Contact us


All 4311 parts are RoHS compliant.
Minimum Order Quantity (MOQ) is one tube or one reel. Parts must be ordered in multiples of the MOQ.
Samples are available for qualified applicants.
Pricing is subject to change.

Design Notes (as PDF files)

Design Note 00A   Basic Compressor/Limiter Design (113k) (formerly Application Note 100A)

Design Note 01A   The Mathematics of Log-Based Dynamic Processors (64k) (formerly Application Note 101A)

Design Note 02  Digital Gain Control with Analog VCAs (106k) (formerly Application Note 102)

Design Note 03  Signal Limiter for Power Amplifiers (95k) (formerly Application Note 103)

Design Note 04   Improving Loudspeaker Signal Handling Capability (217k) (formerly Application Note 104)

Design Note 05   A Low Parts Count, Two-Slope Compressor (78k) (Application Note 105)

Design Note 100   A Fully Adjustable Noise Gate (69k)

Design Note 101   Peak Detection with the THAT4301 (37k)

Design Note 102   Adjustable Ducker using the THAT 4301 (76k)

Design Note 107/111   A Simple Effective Soft-Knee Compressor / Limiter (81k)

Design Note 108   Single Chip Automatic Gain Control  (73k)

Design Note 112   LED Bar-Graph Compression Indictor (83k)

Design Note 113   THAT4301 Gain Reduction Indicator (33k)

Design Note 114   Adaptive Attack and Release Rates using THAT RMS Detectors (48k)

Design Note 115   Fully Adjustable Compressor/Limiter (46k)

Design Note 116   Techniques for Stereo Volume Control (126k)

Design Note 117   Input Limited for ADCs (120k)

Design Note 118   High Performance Stereo AGC (90k)

Design Note 119   Wide Ranging dB Meter (177k)

Design Note 125   The “One Knob Squeezer”  (90k)

Design Note 128   What’s a PTAT Temp. Coefficient, & Where Does It Come From?  (64k)

Design Note 131   Dealing with the PTAT Coefficient (75k)

Design Note 132   Alternate Method of Indicating Compression (52k)

Related Products

Other Analog Engines
THAT 4301 High performance Analog Engine for dual supply voltages. 4301 Datasheet
THAT 4305 Low-cost basic Analog Engine for dual supply voltages. 4305 Datasheet
THAT 4320 Low-voltage, low-power versatile Analog Engine for single supply voltages. 4320 Datasheet
THAT 4315 Low-voltage, low-power basic Analog Engine for single supply voltages. 4315 Datasheet
THAT 4316 Very low-voltage, low-power basic Analog Engine for single supply voltages. 4316 Datasheet
Voltage Controlled Amplifiers (VCAs)
THAT 2180 Series Pre-trimmed Blackmer VCAs 2180 Series Datasheet
THAT 2181 Series Trimmable Blackmer VCAs 2181 Series Datasheet
THAT 2162 Dual Blackmer VCAs 2162 Datasheet

Additional Resources

Analog Engine Selector
A side by side comparison of the features and specifications of our Analog Engine dynamic processor ICs.

The History of VCAs – THAT Blackmer® VCAs are the successors to the original dbx® line of VCAs. Their development for professional audio use has a long history, and can provide some insight into the care and feeding of these essential devices.

4311 Material Data Declaration Sheet
Material Data Declaration Sheets (MDDS) disclose the hazardous materials in our integrated circuits as required by the European RoHS directive.