CA3080 vs LM13700: Exploring the Differences and How to Choose

Introduction

In this article, our team Avaq offers a comparative analysis between the CA3080 and LM13700 integrated circuits, essential components in electronic engineering. It outlines the distinct features and applications of each, emphasizing the critical need to discern their differences. By delving into their functionalities, applications, and performance variations, this piece aims to assist electronic enthusiasts and engineers in making informed choices for their circuit designs based on the unique attributes of these ICs.

Here's the video about 3080 vs 13700 explained,

 

Understanding the CA3080

1. Introduction to the CA3080 IC

The CA3080 and CA3080A ICs mark a significant advancement in Gatable-Gain Blocks, leveraging the distinctive operational-transconductance-amplifier (OTA) concept elucidated in Application Note ICAN-6668, "Applications of the CA3080 and CA3080A High-Performance Operational Transconductance Amplifiers." These components are characterized by a differential input and a single-ended, push-pull, class A output configuration. Additionally, they incorporate an amplifier bias input that offers adaptability for both gating and linear gain control functionalities.

 

Notably, they exhibit a high output impedance, and their transconductance (gM) directly corresponds to the amplifier bias current (IABC), ensuring precision in their functionality. Highlighting an exceptional slew rate of 50V/µs, these components excel in multiplexer applications and swift unity-gain voltage followers, operating with power consumption only in the "ON" channel state.

Moreover, the CA3080A variant is rated for full military-temperature range operation (-55oC to +125oC) and is finely tuned for sample-hold, gain-control, and multiplexing applications. Expanding their utility, operational transconductance amplifiers, as described in Application Note AN6048, "Some Applications of a Programmable Power Switch/Amplifier" (CA3094, CA3094A, CA3094B), also prove beneficial in programmable power-switch scenarios, showcasing their versatility across various electronic applications.

2. CA3080 Pinout

Pinout Details

Pin No.	Description	Pin Name
1, 8	Not connected	NC
2	Inverting Input	IN -
3	Non-inverting Input	IN +
4	Ground	GND
5	Amplifier bias input	Ibias
6	Output	Output
7	Voltage supply	Vcc

3. Specifications and Features

• Achieving a Slew Rate of 50V/µs (Unity Gain, Compensated)
• Adjustable Power Consumption Ranging from 10µW to 30µW
• Versatile Supply Voltage Range: ±2V to ±15V
• Complete Adjustability of Gain: From 0 to gMRL Limit
• Precise gM Spread: CA3080: Maintaining a Tight Ratio of 2:1
• Extending gM Linearity Across 3 Decades

4. Applications in different electronic circuits or systems

Applications

• Sample and Hold Circuits: Utilized for maintaining and storing an analog signal at a specific point in time, crucial in analog-to-digital conversion processes, waveform capturing, and signal processing applications.
• Multiplier Configurations: Employed in analog multiplier circuits, facilitating the multiplication of two input signals, prevalent in modulation, frequency mixing, and various signal processing tasks.
• Multiplexer Operations: Integral component in multiplexers, enabling the selection and routing of multiple analog signals through a single channel or line, common in data acquisition systems and telecommunications.
• Comparator Functions: Engaged in comparison tasks, where it evaluates two voltage signals and determines their relationship, pivotal in instrumentation, threshold detection, and feedback control systems.
• Voltage Follower Applications: Deployed as unity-gain buffers, maintaining the same voltage as the input signal, minimizing load effects, and widely utilized in impedance matching, signal buffering, and isolation circuits.

Applications in Different electronic circuits

LEAKAGE CURRENT TEST CIRCUIT

DIFFERENTIAL INPUT CURRENT TEST CIRCUIT

THE CA3080 AND CA3080A IN A UNITY-GAIN

VOLTAGE FOLLOWER CONFIGURATION AND ASSOCIATED WAVEFORM

Understanding the LM13700

1. Introduction to the LM13700 IC

The LM13700 stands as an integrated circuit comprising two current-controlled operational transconductance amplifiers (OTAs), each featuring differential inputs and a push-pull output. Differing from a standard op-amp, an OTA operates with voltage in and current out, and its behavior can be programmed via the IABC pin. Linearizing diodes at the input serve to minimize distortion and enable higher input levels. Specifically engineered darlington output buffers complement the OTA's wide dynamic range.

This chip finds extensive utility in audio electronics, notably in analog synthesizer circuits such as voltage-controlled oscillators, voltage-controlled filters, and voltage-controlled amplifiers. The darlington output buffers on the LM13700 differ from those on the LM13600 as their bias currents, and hence their output DC levels, operate independently of the IABC pin. This characteristic can result in superior performance compared to the LM13600, particularly in audio applications.

2. LM13700 IC Pinout

Pin Functions

Pin No.	I/O Description	Name
1, 16	A Current bias input	Amp bias input
7, 10	A Buffer amplifier input	Buffer input
8, 9	A Buffer amplifier output	Buffer output
2, 15	A Linearizing diode bias input	Diode bias
3, 14	A Positive input	Input+
4, 13	A Negative input	Input–
5, 12	A Unbuffered output	Output
11	P Positive power supply	V+
6	P Negative power supply	V-

3. Technical specifications and features

Specifications

• Number of channels: 2
• Total supply voltage (max): 36V
• Total supply voltage (min): 10V
• Rail-to-rail: No
• Gain-Bandwidth Product (GBW): 2 MHz
• Slew rate: 50 V/µs
• Offset voltage (max) at 25°C: 4 mV
• Quiescent current per channel (typ): 1.3 mA
• Rating: Catalog
• Operating temperature range: 0 to 70°C
• Offset drift (typ): 0 µV/°C
• Maximum input bias current: 5,000,000 pA
• Common-Mode Rejection Ratio (CMRR) (typ): 110 dB
• Output current (typ): 0.02 A
• Architecture: Bipolar
• Input common mode headroom (to negative supply): 0V
• Input common mode headroom (to positive supply): 0V
• Output swing headroom (to negative supply): 0V
• Output swing headroom (to positive supply): 0V

Features

• Adjustable gM Across 6 Decades
• Outstanding gM Linearity
• Precise Matching Between Amplifiers
• Linearizing Diodes for Minimized Output Distortion
• High-Impedance Buffers
• Elevated Output Signal-to-Noise Ratio

4. Applications

• Current-Controlled Amplifiers
• Stereo Audio Amplifiers
• Current-Controlled lmpedances
• Current-Controlled Filters
• Current-Controlled Oscillators
• Multiplexers
• Timers
• Sample-and-Hold Circuits

Differences between CA3080 and LM13700

Specifications

Specification	CA3080	LM13700
Functionality	Gatable-Gain Block	Dual Operational Transconductance Amplifiers (OTAs)
Configuration	Single operational transconductance amplifier	Dual OTAs within a single chip
Outputs	Push-pull, class A output	Push-pull output for each OTA
Input/Output Channels	Single-channel	Dual-channel (two integrated OTAs)
Supply Voltage Range	±2V to ±15V	±5V to ±18V
Slew Rate	50V/µs	50V/µs
Offset Voltage (max)	4 mV	-
Gain-Bandwidth Product (GBW)	2 MHz	-
Input Bias Current (max)	-	5,000,000 pA (per channel)
Common-Mode Rejection Ratio (CMRR)	-	110 dB (typical)
Operating Temperature Range	0 to 70°C	0 to 70°C

Main Difference between CA3080 and LM13700

Functionality:

• CA3080: Designed as a Gatable-Gain Block primarily used in voltage-controlled amplifiers, filters, and oscillators.
• LM13700: Consists of dual Operational Transconductance Amplifiers (OTAs), commonly applied in audio circuits like synthesizers for filters, oscillators, and amplifiers.

Configuration:

• CA3080: Features a single operational transconductance amplifier.
• LM13700: Integrates two OTAs within a single chip, providing dual-channel capabilities.

Outputs:

• CA3080: Offers a push-pull, class A output.
• LM13700: Presents push-pull outputs for each OTA, allowing independent control.

Components Usage:

• CA3080: Leverages the operational transconductance amplifier concept for specific applications like gating or linear gain control.
• LM13700: Utilizes OTAs with voltage in and current out behavior, programmable through the IABC pin.

Applications:

• CA3080: Suited for systems requiring gatable gain blocks, multiplexers, and voltage followers.
• LM13700: Widely used in audio electronics, particularly in synthesizer circuits for its OTA-based functionalities in filters, oscillators, and amplifiers.

Number of Channels:

• CA3080: Typically a single-channel device.
• LM13700: Houses two OTAs, providing dual-channel capabilities.

Advantages and disadvantages of each IC CA3080 and LM13700

CA3080

Advantages:

• Gatable-Gain Block: Specifically designed for gatable gain applications, useful in voltage-controlled amplifiers and filters.
• Low Power Consumption: Efficient power usage when compared to some alternatives.
• High Slew Rate: 50V/µs slew rate makes it suitable for multiplexers and fast voltage followers.
• Excellent for Audio: Well-suited for audio applications and voltage-controlled systems.

Disadvantages:

• Limited Functionality: Specialized for gatable gain applications, limiting versatility in broader circuits.
• Single Channel: Typically operates as a single-channel device, constraining applications requiring multiple channels.

LM13700

Advantages:

• Dual OTAs: Contains two OTAs within a single chip, providing dual-channel capabilities.
• Audio Circuit Applications: Widely used in audio systems for filters, oscillators, and amplifiers.
• Versatile Programming: Programmable OTAs via the IABC pin, allowing flexibility in design.
• High Input Impedance: Suitable for various input signal configurations.

Disadvantages:

• Higher Power Consumption: Compared to some alternatives, it may consume relatively more power.
• Complexity: Dual-channel design might increase circuit complexity in some applications.

Key Factors Influencing the Choice between CA3080 and LM13700

When choosing between the CA3080 and LM13700 integrated circuits, several key factors come into play:

CA3080:

• Gatable Gain Applications: Ideal for circuits requiring gatable gain blocks, voltage-controlled amplifiers, and filters.
• Single-Channel Requirement: Suitable when a single-channel operational transconductance amplifier suffices for the application.
• Low Power Consumption: If power efficiency is a priority compared to other alternatives.
• Specific Audio Applications: Suited for audio-related circuits like voltage-controlled systems.

LM13700:

• Dual OTA Requirement: Need for dual-channel operational transconductance amplifiers within a single chip.
• Audio Circuit Design: Specifically useful in audio systems for filters, oscillators, and amplifiers.
• Versatile Programming: When the flexibility of programmable OTAs via the IABC pin is desired.
• Higher Input Impedance: Applications that benefit from higher input impedance configurations.

Datasheet PDF

ca3080

lm13700

Conclusion

In exploring the differences between the CA3080 and LM13700 integrated circuits, it becomes evident that each possesses unique characteristics tailored for distinct applications. The CA3080, designed as a specialized gatable gain block, excels in single-channel configurations, making it particularly suitable for voltage-controlled amplifiers and filters. Its emphasis on power efficiency and suitability for audio systems highlights its niche in specific electronic designs.

Conversely, the LM13700, housing dual Operational Transconductance Amplifiers (OTAs) within a single chip, stands out for its versatility in dual-channel applications, especially in audio circuitry for filters, oscillators, and amplifiers. Its programmability via the IABC pin and higher input impedance expand its usability in various circuit configurations.

Selecting between these ICs necessitates a deep understanding of the circuit requirements. The CA3080's strengths lie in its focused gatable gain functionality and efficiency, while the LM13700's advantage lies in its dual-channel versatility and adaptability in audio circuits.

Ultimately, the best-suited IC depends on the specific demands of the electronic system. Careful consideration of factors like channel requirements, power efficiency, and intended applications ensures the optimal choice, enabling seamless integration and superior performance within the targeted circuit design.