CA3080 Operational Transconductance Amplifier (OTA)

Overview

The CA3080 and CA3080A are high-performance operational transconductance amplifiers (OTAs) designed for precision analog signal processing. These devices implement a gatable-gain block architecture, leveraging the unique OTA concept detailed in Application Note AN6668. The CA3080 series features a differential input stage and a single-ended, push-pull, class A output, making it highly versatile for a wide range of analog applications. A key feature of these devices is the amplifier bias input, which allows for gating or linear gain control, providing flexibility in circuit design.

The transconductance (g_M) of the CA3080 is directly controllable, enabling precise adjustment of gain and power consumption. With a high output impedance and excellent linearity, these OTAs are ideal for applications requiring variable gain, signal modulation, or analog computation.

Features

• High Slew Rate: 50V/µs (unity gain, compensated)
• Adjustable Power Consumption: Ranges from 10µW to 30µW for low-power applications
• Wide Supply Voltage Range: Operates from ±2V to ±15V, accommodating various power requirements
• Fully Adjustable Gain: Gain can be set from 0 to the g_MR_L limit
• Tight Transconductance (g_M) Spread:
  • CA3080: 2:1 ratio
  • CA3080A: 1.6:1 ratio (improved consistency)
• Extended g_M Linearity: Maintains linearity across three decades of input signal
• High Output Impedance: Enables easy interfacing with external loads
• Class A Output Stage: Provides low distortion and high signal fidelity

Applications

The CA3080 and CA3080A are widely used in analog signal processing and control systems. Key applications include:

• Sample and Hold Circuits: Utilizes the OTA's fast response and adjustable gain for accurate signal sampling.
• Analog Multipliers: Leverages the linear transconductance for precise multiplication of input signals.
• Multiplexers: The gating capability allows for efficient signal routing in analog multiplexing applications.
• Comparators: High slew rate and differential input make it suitable for fast signal comparison.
• Voltage Followers: Provides high input impedance and low output impedance for buffering applications.
• Voltage-Controlled Amplifiers (VCAs): The bias input enables voltage-controlled gain adjustment.
• Waveform Generators: Used in oscillator circuits for generating precise waveforms.

Electrical Characteristics

Absolute Maximum Ratings

• Supply Voltage (V_CC to V_EE): ±18V
• Input Voltage Range: ±V_CC
• Output Short-Circuit Duration: Continuous (with proper heat sinking)
• Operating Temperature Range: -55°C to +125°C (military-grade versions available)

Typical Performance Characteristics

• Transconductance (g_M): 9.2mS (typical at I_ABC = 500µA)
• Input Offset Voltage: ±2mV (max)
• Input Bias Current: 1.2µA (typical)
• Bandwidth (Unity Gain): 2MHz (typical)
• Common-Mode Rejection Ratio (CMRR): 90dB (typical)
• Power Supply Rejection Ratio (PSRR): 80dB (typical)

Package Information

The CA3080 and CA3080A are available in multiple package options to suit different assembly requirements:

• 8-Pin Metal Can (TO-99): Hermetically sealed for high-reliability applications.
• 8-Pin Plastic DIP (PDIP): Cost-effective solution for commercial applications.
• 8-Pin SOIC (Surface Mount): Compact footprint for space-constrained designs.

Pin Configuration (8-Pin DIP/SOIC)

• Pin 1: Amplifier Bias Input (I_ABC)
• Pin 2: Non-Inverting Input (+IN)
• Pin 3: Inverting Input (-IN)
• Pin 4: Negative Supply (V_EE)
• Pin 5: Output (OUT)
• Pin 6: Positive Supply (V_CC)
• Pin 7: Compensation (COMP)
• Pin 8: Not Connected (NC)

Conclusion

The CA3080 and CA3080A operational transconductance amplifiers offer a unique combination of adjustable gain, high linearity, and versatile control features, making them indispensable in analog circuit design. Their robust performance across a wide supply range and flexible packaging options ensure suitability for both commercial and industrial applications. Whether used in signal processing, modulation, or control systems, the CA3080 series delivers precision and reliability.