Hi-End Headphone Amplifier for DACs Differential Signal input

Simple stereo headphone amplifier for audio DACs required a differential signal. The circuit works with dual +/-5V DC supply, the project can drive load 16 Ohms to 600 Ohms. Headphone amplifier provides output 50mW into 32 Ohms. Signal for the right channel and left channel input is applied to the amplifier through connectors CN1and CN3, respectively. The source such as an audio analyzer or audio digital-to-analog converts (DAC). The positive input from the source connects to the pin labeled I1+/I2+, the negative input from the source connects to the pin labeled I1-/I2-, and the ground connection from the source connects to the center pin of CN1 and CN3, labeled GND. Output connections are provided through the use of the CN2, CN4 provided to power up the board, D1 power LED. OPA1688 or OPA1622 op-amps are good for the applications.

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  • Supply Input +/-5V DC
  • Load 16 Ohms to 600 Ohms (32 Ohms Ideal)
  • Output Load 50mW into 32 Ohms Headphone
  • Frequency Response 20 Hz to 20 kHz

3 Amps power operational amplifier using lm675

Power operational board can drive high current load up to 3Amps, the board helpful to drive Dc Motor, solenoid, Lamp, LED and industrial application. The project built around LM675 power op-amp from texas instruments. All resistors are 1%. Refer datasheet of LM675 for further information.

I Output= VIN X 2.5amps/volt

i.e Iout=1A when VIN=400mV

Trimmer Pot for Max Rout

Download PDF PCB Layout

The LM675 is a monolithic power operational amplifier featuring wide bandwidth and low input offset voltage, making it equally suitable for AC and DC applications.

The LM675 is capable of delivering output currents in excess of 3 amps, operating at supply voltages of up to 48V. The device overload protection consists of both internal current limiting and thermal shutdown. The amplifier is also internally compensated for gains of 10 or greater.


  • 3A Current Capability
  • AVO Typically 90 dB
  • 5 MHz Gain Bandwidth Product
  • 8 V/μs Slew Rate
  • Wide Power Bandwidth 70 kHz
  • 1 mV Typical Offset Voltage
  • Short Circuit Protection
  • Thermal Protection with Parole Circuit (100% Tested)
  • 16V–48V Supply Range ( +/-12 To 24V DC)
  • Wide Common-Mode Range
  • Internal Output Protection Diodes
  • 90 dB Ripple Rejection


Original Circuit from Texas Instruments Data Sheet

Audio line receiver/Studio Grade 2-channel audio line receiver using ina1650

Professional stereo audio line receiver is based on INA1650 device is designed to require a minimum number of external components to achieve data sheet level performance in audio line-receiver applications. Circuit shows the INA1650 used as a differential audio line receiver in split-supply systems that are common in professional audio applications. The line receiver recovers a differential audio signal which may have been affected by significant common-mode noise. The INA1650 is a high common-mode rejection audio line receiver from the Sound Plus line of audio Amplifier products from Texas Instruments.

  • Supply +/- 15V DC
  • Common-Mode Rejection Ratio (CMRR) VIN = 1 Vrms at 1 kHz –90 dB
  • THD+N at 1 kHz VIN = +22 dBu –120 dB
  • Second Harmonic – VOUT = 10 Vrms, F = 1 kHz –134.35 dBc


  1. C1,C2 10uF/25V SMD 1210
  2. C3, C7, C10, C12 10uF/35V Non Polar
  3. All Resistors SMD 0805 5%
  4. C6,C11  10uF/35V SMD 1206
  5. C2, C5, C8, C9, SMD 0805
  6. LED SMD 0805
  7. INA1650

The dual-channel INA1650 and single-channel INA1651 (INA165x) SoundPlus™ audio line receivers achieve an extremely-high common-mode rejection ratio (CMRR) of 91 dB while maintaining an ultra-low THD+N of –120 dB at 1 kHz for 22-dBu signal levels. Precision matching of on-chip resistors gives the INA165x devices excellent CMRR performance. These resistors have matching that is far superior compared to external components and are immune to mismatches introduced by printed circuit board (PCB) layout. Unlike other line receiver products, the INA165x CMRR is characterized over temperature and tested in production to deliver consistent performance in a wide variety of applications.

The INA165x devices operate over a very-wide-supply range of ±2.25 V to ±18 V, on 10.5 mA of supply current. In addition to the line-receiver channels, a buffered mid-supply reference output is included, making the INA165x configurable for dual- or single-supply applications. The mid-supply output can be used as a bias voltage for other analog circuitry in the signal chain. These devices are specified from –40°C to +125°C.


  • High Common-Mode Rejection:
  • 91 dB (Typical)
  • High Input Impedance: 1-MΩ Differential
  • Ultra-Low Noise: –104.7 dBu, Unweighted
  • Ultra-Low Total Harmonic Distortion + Noise:
  • –120 dB THD+N (22 dBu, 22-kHz Bandwidth)
  • Wide Bandwidth: 2.7 MHz
  • Low Quiescent Current: 6 mA (INA1651, Typical)
  • Short-Circuit Protection
  • Integrated EMI Filters
  • Wide Supply Range: ±2.25 V to ±18 V

Studio-Grade Fully Balanced Stereo Headphone Amplifier Using LME49600 and BA4560

This little project will drive the signal from your balanced Audio source and increase both its volume and detail.  The project has been designed for professional audio lovers, this project is easy to make and low-cost solution for audio professionals, The LME49600 , LME49720 and  BA4560 ICs are used to design the project, the project can drive 16 Ohms or 32 Ohms headphones, The project  provides high-quality sound and it can be used in professional studios.


  • Supply 15V Dual ( +/-12V DC)
  • Current 200mA
  • Output Load 16/32 Ohms Headphones
  • Input Balanced Stereo
  • On-Board Power LED
  • 5MM EP Stereo Socket Provided for Headphone
  • On Board Potentiometer Helps to Adjust the Gain
  • Audio Input Using Screw Terminals
  • Screw Terminals for Supply Input

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Low Noise Dual Supply Voltage Operational Amplifier – BA4560F

General-purpose BA4558 / BA4560 / BA15218 / BA14741 / BA15532 / BA4510 family and high-reliability BA4558R / BA4560R / BA4564R / BA4580R / BA4584 / BA4584R / BA8522R / BA2115 family integrate two or four independent Op-Amps on a single chip Especially, this series is suitable for any audio applications due to low noise and low distortion characteristics and are usable for other many applications by wide operating supply voltage range. BA4558R / BA4560R / BA4564R / BA4580R / BA4584R / BA8522R / BA2115 are high-reliability products with extended operating temperature range and high ESD tolerance.


The LME49600 is a high performance, low distortion high fidelity 250mA audio buffer. The LME49600 is designed for a wide range of applications. It can be used inside the feedback loop of op amps. The LME49600 offers a pin-selectable bandwidth: a low current, 110MHz bandwidth mode that consumes 7.3mA and a wide 180MHz bandwidth mode that consumes 13.2mA. In both modes the LME49600 has a nominal 2000V/μs slew rate. Bandwidth is easily adjusted by either leaving the BW pin unconnected or connecting a resistor between the BW pin and the VEE pin.The LME49600 is fully protected through internal current limit and thermal shutdown.


The LME49720 device is part of the ultra-low distortion, low noise, high slew rate operational amplifier series optimized and fully specified for high performance, high fidelity applications. Combining advanced leading-edge process technology with state-of-the-art circuit design, the LME49720 audio operational amplifiers deliver superior audio signal amplification for outstanding audio performance. The LME49720 combines extremely low voltage noise density (2.7nV/√Hz) with vanishingly low THD+N (0.00003%) to easily satisfy the most demanding audio applications.

Electret Capsule Micro-Phone Pre-Amplifier Using TLV6741 Op-Amp

I am here with one more electret microphone preamplifier. This circuit uses an op-amp in a trans-impedance amplifier configuration to convert the output current from an electret capsule microphone into an output voltage. The common mode voltage of this circuit is Constant and set to mid-supply eliminating any input–stage cross over distortion, Circuit and description of the project from Texas Instruments Application. The circuit is based on TLV6741 Op-Amp from Texas Instruments.


  • Supply 5V DC
  • Input Pressure 100dB SPL(2Pa)
  • Output Voltage 1.228V
  • Frequency Response Deviation @20Hz>-0.5dB,@20Khz>-0.1dB

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Microphone Parameter

  • Sensitivity @94dB SPL (1Pa) >>-35+/-4dBV
  • Current Consumption (Max)>>0.5mA
  • Impedance>> 2.2KOhms
  • Standard Operating Voltage 2V

Op-Amp TLV6741

The TLV6741 operational amplifier (op-amp) is a general-purpose CMOS op-amp that provides low noise of 3.7 nV/√Hz and a wide bandwidth of 10 MHz. The low noise and wide bandwidth make the TLV6741 device attractive for a variety of precision applications that require a good balance between cost and performance. Additionally, the input bias current of the TLV6741 supports applications with high source impedance. The robust design of the TLV6741 provides ease-of-use to the circuit designer due to its unity-gain stability, integrated RFI/EMI rejection filter, no phase reversal in overdrive conditions and high electrostatic discharge (ESD) protection (1-kV HBM). Additionally, the resistive open-loop output impedance makes it easy to stabilize with much higher capacitive loads. This op-amp is optimized for low-voltage operation as low as 2.25 V (±1.125 V) and up to 5.5 V (±2.75 V), and is specified over the temperature range of –40°C to +125°C. The single-channel TLV6741 is available in a small size SC70-5 package.

Balanced Audio head-phone amplifier ( Balanced audio monitor)

Useful audio device for audio professionals, tiny board is a balanced headphone monitor, based on BA4560 op-amp, project works with 12V DC supply, Female XLR connector helps to feed balanced audio input, male XLR connector for parallel balanced signal output, and 3.5MM Stereo EP socket provided to connect headphone, easy supply input using standard DC socket, onboard potentiometer provided to adjust the gain.


  • Supply 12V DC
  • DC Socket for Supply Input Or CN4 Header Connector
  • 3.5MM EP Socket for Headphone
  • Load: 32 Ohms Headphone
  • XLR Female: Balanced Audio Signal Input
  • XLR Male: Balanced Audio Output
  • D1 Power LED


  • C1, C2 10uF/25V Bipolar Capacitors,
  • C11 220uF/16V , C10 470uF/16V, C1,C2 40uF/25V  Electrolytic Capacitors
  • All Other Capacitors and Resistors SMD 0805
  • IC BA4560 SMD SO8 www.rhom.com

Balanced Audio Line Driver (Unbalance to Balance Audio Signal Converter) Using DRV135/SSM2142

The Mini board converts unbalance Audio signal into balance audio signal, the project is based on SSM2142 or DRV135 IC which are differential output amplifier that converts a single ended audio signal input to a balanced output pair. This balanced audio driver consists of high-performance op-amps with on-chip precision resistors. They are fully specified for high-performance audio applications and have excellent ac specifications, including low distortion (0.0005% at 1 kHz) and high slew rate (15 V/µs).

The on-chip resistors are laser-trimmed for accurate gain and optimum output common-mode rejection. Wide output voltage swing and high output drive capability allow use in a wide variety of demanding applications. They easily drive the large capacitive loads associated with long audio cables. Used in combination with the INA134 or INA137 differential receivers, they offer a complete solution for transmitting analogue audio signals without degradation.

Note: SSM2142 and DRV135 pin to pin compatible, any of this IC can be used.


  • Supply Dual 15V DC (+/-15V DC)
  • Balanced Output
  • Low Distortion: 0.0005% at f = 1 kHz
  • Wide Output Swing: 17Vrms into 600 Ω
  • High Capacitive Load Drive
  • High Slew Rate: 15 V/µs
  • Low Quiescent Current: ±5.2 mA IC
  • Companion to Audio Differential Line Receivers
  • Header Connector Provided for Audio Signal Input
  • Header Connector for Supply Input
  • Audio Output from XLR Connector
  • Input Aux Audio Signal
  • On-Board Power LED


  • Audio Differential Line Drivers
  • Audio Mix Consoles
  • Distribution Amplifiers
  • Graphic Equalizers
  • Dynamic Range Processors
  • Digital Effects Processors
  • Hi-Fi Audio Equipment’s


  1. Capacitor C5, C10, C7 Non-Polar Capacitors
  2. All Resistors SMD 0805 5%
  3. LED SMD 0805
  4. C1,C3,C7 Electrolytic Capacitors SMD
  5. Output XLR Male Connector
  6. ETH Chassis Ground

Design Requirement

Consider a design with the goal of deferentially transmitting a single ended signal of up to 22.2 dBu through 500 ft of cable with no load at the receiving side. The signal at the end of the cable should have no more than 0.002 per cent of total harmonic distortion plus noise (THD+N) at 10 kHz and less than 0.0005 percent of THD+N for frequencies between 20 Hz and 1 kHz.

The system is required to put out a single-ended signal 0 dB with respect to the input signal and accommodate inputs with a peak to RMS ratios of up to 1.5 for the maximum 22.2 dBu range established above.

The DRV134 and DRV135 were designed for enhanced ac performance. Very low distortion, low noise, and wide bandwidth provide superior performance in high-quality audio applications. Laser-trimmed matched resistors provide optimum output common-mode rejection (typically 68dB), especially when compared to circuits implemented with op-amps and discrete precision resistors. In addition, high slew rate (15 V/μs) and fast settling time (2.5 μs to 0.01%) ensure an excellent dynamic response. The DRV134 and DRV135 have excellent distortion characteristics. As shown in the distortion data provided in

the Typical Characteristics section, THD+Noise is below 0.003% throughout the audio frequency range under various output conditions. Both differential and single-ended modes of operation are shown. In addition, the optional 10μF blocking capacitors used to minimize VOCM errors have virtually no effect on performance. Measurements were taken with an Audio Precision System One (with the internal 80 kHz noise filter

Example Circuit With Balanced Line Receiver



Design Description

This design inverts the input signal, Vi, and applies a signal gain of –2V/V. The input signal typically comes from a low-impedance source because the input impedance of this circuit is determined by the input resistor, R3. The common-mode voltage of an inverting amplifier is equal to the voltage connected to the non-inverting node, which is ground in this design. D1 indicates the power, all connection can be done using CN1 header connector, Capacitors, Resistors, LEDs are SMD components size 0805. Op-Amp TLV170 from Texas Instruments.

D1=Power LED, CN1= 6 Pin male header connector

ViMIN=-7V, ViNMAX=7V, VoMIN=–14V, VoMAX=14V, F=3KHZ, V+=15V, V-=-15V

Design Notes

  1. Use the op amp in a linear operating region. Linear output swing is usually specified under the AOL test conditions. The common-mode voltage in this circuit does not vary with input voltage.
  1. The input impedance is determined by the input resistor. Make sure this value is large when compared to the source’s output impedance.
  1. Using high value resistors can degrade the phase margin of the circuit and introduce additional noise in the circuit.
  1. Avoid placing capacitive loads directly on the output of the amplifier to minimize stability issues.
  2. Small-signal bandwidth is determined by the noise gain (or non-inverting gain) and op amp gainbandwidth product (GBP). Additional filtering can be accomplished by adding a capacitor in parallel to R1. Adding a capacitor in parallel with R1 will also improve stability of the circuit if high value resistors are used.
  1. Large signal performance may be limited by slew rate. Therefore, check the maximum output swing versus frequency plot in the data sheet to minimize slew-induced distortion.
  1. For more information on op amp linear operating region, stability, slew-induced distortion, capacitive load drive, driving ADCs, and bandwidth please see the Design References section.




Application Courtesy of Texas Instruments





Pro Audio Microphone Pre-Amplifier Using INA217 and OPA2137

Its simple Tiny Pro-microphone Pre-Amplifier using INA217 instruments amplifier and OPA2137 op-amp. Circuit has been designed using SMD components, 3 Pin female XLR connector has been used for direct micro-phone input.

The board has been design around INA217 low distortion, low noise instrumentation amplifier. The INA217 is ideal for low-level audio signals such as balanced low-impedance microphones. Many industrial, instrumentation, and medical applications also benefit from its low noise and wide bandwidth. Unique distortion cancellation circuitry reduces distortion to extremely low levels, even in high gain. The INA217 provides near-theoretical noise performance for 200Ω source impedance. The INA217 features differential input, low noise, and low distortion that provides superior performance in professional microphone amplifier applications. An OPA2137 op-amp used as a feedback to eliminate the offset voltage. Phantom power is not part of the circuit its just for reference. 


  • Supply Dual +/-15V DC
  • Output Unbalance Single Ended
  • PR1 Gain Adjust G=1+10000/Rg PR1









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