Tag Archives: Amplifier

How to use a fully differential amplifier as a level shifter

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Loren Siebert @ ti.com discuss about how to interface signals that have a reference voltage that isn’t 0V while preserving the DC information.

Many signal paths are direct current (DC)-coupled, and this can lead to challenges when different portions of the signal path require different operating conditions. Many portions of a signal path are ground-referenced, where a signal varies at about an average or mid value of 0V. If all signals had the same reference voltage, DC coupling would be very easy. Unfortunately, that is not the case. Devices operating from a single supply like mixers or analog-to-digital converters (ADCs) will typically have a reference voltage (common mode) that is not 0V. Interfacing these devices while preserving DC information can be challenging.

How to use a fully differential amplifier as a level shifter – [Link]

3W Stereo Audio Amplifier using TDA7266D


Tiny stereo audio amplifier board has been designed around SMD TDA7266D IC from ST. The TDA7266D is a dual bridge amplifier specially designed for Portable Audio, LCD TV/Monitor, PC Motherboard, and TV applications. This circuit provides high quality audio output of 3W approx. on each channel with standard audio signal input. The circuit works with 3.5V to 5V. Due to low supply input this amplifier is suitable for small size audio gadgets and portable audio applications like MP3 player, Voice messaging system, Warning signals, Annunciator etc.


  • Supply voltage range 3.5 to 5v (maximum supply 5v due to small pcb and small thermal area)
  • Output power 3+3w @thd = 10%, rl = 8ω, vcc = 3.7v (3w approx.)
  • Single supply
  • Minimum external components no svr capacitor no bootstrap no boucherot cells internally fixed gain
  • Mute functions (jumper close)
  • Short circuit protection
  • Thermal overload protection

3W Stereo Audio Amplifier using TDA7266D – [Link]

F1200 Low-noise Digital IF VGA with FlatNoise

The F1200 of an IDT is a digitally controlled intermediate frequency differential variable gain amplifier that adjusts the gain either dynamically or as a one-time channel gain setting. The device has extremely low noise figure over the entire gain control range. It is packaged in compact 5×5 Thin QFNs with 200 ohm differential input and output impedances for ease of integration into the receiver lineup with IF frequencies up to 300MHz.

The device has exceptional DNL and INL simplifying digital compensation. It has extremely low Harmonic, IM2, and IM3 distortion that is necessary to drive an ADC directly in an IF sub-sampling application. The F1200 acts to enhance system SNR when VGA gain is reduced. The F1200 noise figure (NF) degrades only slightly (NF slope ~ -0.16 dB/dB) over a 13 dB control range while holding the output IP3 approximately constant. The resultant improvement in noise can enhance the system SNR up to 2 decibels at low gain settings relative to a standard VGA.

This design is used in either transmitter or receiver to add an adjustable gain element to the signal chain by increasing or decreasing the attenuation value. Other applications include base station, diversity receivers, digital pre-distortion, μ-wave point-to-point radios and public safety receivers.

F1200 Low-noise Digital IF VGA with FlatNoise – [Link]

LM386 SMD Audio Amplifier Module


The Tiny Audio Amplifier MODULE is a good choice for battery operation. It is based on LM386 IC, useful in various applications like robotics, science projects, intercom, FM radio and many more.


  • Power Supply 6V-9V
  • 300mW Output @ 8Ohms Load
  • On Board Potentiometer for Audio Level Adjust
  • Header Connecter for Supply, Signal in and Speaker
  • On Board Power LED
  • Input: Standard Audio Signal

LM386 SMD Audio Amplifier Module – [Link]

Tutorial on the Theory, Design and Characterization of a CMOS Transimpedance Amplifier

In this episode, Shahriar and Shayan discuss the design and characterization of a deceptively simple CMOS inverter-based transimpedance amplifier. The the large and small signal behavior of the CMOS inverter is discussed and measured using the Keithley 2450 and 2460 source meters. The transient response is also measured using a Keysight MSO-S series oscilloscope.

The small signal gain of the circuit is calculated from small signal parameters which are extracted directly by measuring the devices I/V characteristics. The NMOS/PMOS devices used are from an ADL1105 quad-discrete transistor IC. Through the use of a shunt-shunt feedback, the CMOS amplifiers is converted to a transimpedance amplifier which is capable of amplifying the current from a photo-detector diode by a gain of 30kV/A. The feedback theory is used to calculate the gain of the amplifier. The slides for this tutorial can be downloaded from The Signal Path website.

Tutorial on the Theory, Design and Characterization of a CMOS Transimpedance Amplifier – [Link]

1.6W Mono Audio Amplifier


1.6W Mono Audio Amplifier Project is based on TDA7231, which is class AB power amplifier with a wide range of supply.

  • Power supply: 5 To 12 VDC
  • Output: 1.6 W, 4 Ω / 1 W, 8 Ω
  • Low crossover distortion, soft clipping
  • PR1 Preset for Volume Adjust
  • Terminal pins for connecting power supply, input and output
  • Power On/OFF Switch
  • Power-On LED indicator
  • Four mounting holes of 3.2 mm each
  • PCB dimensions 36 mm x 52 mm

1.6W Mono Audio Amplifier – [Link]

ARC Digital Amplifier


Enjoy high-end sound quality for all your music with this small and modern digital amplifier.

The ARC was made to bridge the gap between high-end sound quality and the world of digital music. Designed as the perfect receiver and amplifier, this ultra-compact unit provides high-resolution USB audio streaming capabilities, high quality aptX Bluetooth audio and astonishingly detailed sound. For a great listening experience and immersive sound, all you need is a set of speakers and the ARC. Done.

ARC Digital Amplifier – [Link]

Understanding silicon circuits: inside the ubiquitous 741 op amp


Ken Shirriff’s blog looks inside the famous 741 OPMAP and discuss how it’s made and how it’s working:

The 741 op amp is one of the most famous and popular ICs[1] with hundreds of millions sold since its invention in 1968 by famous IC designer Dave Fullagar. In this article, I look at the silicon die for the 741, discuss how it works, and explain how circuits are built from silicon.

Understanding silicon circuits: inside the ubiquitous 741 op amp – [Link]

Introduction to OPAMPs and Applications

Operational amplifiers (OPAMPs) are high performance differential amplifiers in integrated form that can be used in many different ways. A typical OPAMP has a non-inverting input, an inverting input, two dc power pins, one output pin and a few other fine-tuning pins. On the following image you can see a typical diagram of an operational amplifier.

The basic OPAMP operation is simple. If the voltage applied to the inverting input is greater than the voltage applied to the non-inverting input then the output saturates to the negative supply voltage. In addition, if the voltage applied to the non-inverting input is greater than the voltage applied to the inverting input, then the output saturates at positive supply voltage.

This operation mode is limited and doesn’t give us the full idea behind OPAMP operation. The trick to make an OPAMP more useful is to provide negative feedback from the output to the inverting input. In the image below we see an OPAMP with negative feedback working as an inverting amplifier.

In this configuration a part of the output voltage is fed back to the inverting input and thus the gain of the OPAMP can be controlled and output isn’t saturating. The gain of such an amplifier is controlled by the two resistors Rf and Rin. The minus means that the output is inverted relative to input.

By adding more components on the feedback loop, different OPAMP circuits can be made, such voltage regulator circuits, current to voltage converters, oscillators, filters etc.

Beside the negative feedback, a positive feedback can be used. This way the OPAMP is driven toward saturation and works in either +Vs or –Vs output range. Applications of positive feedback is on comparator circuits and oscillators. (more…)

Narrowband RF Power Amplifier (520MHz)

The RF power amplifier stage is usually the final active block of any electronic system that is transmitting RF power. Relatively low power RF signals are amplified to produce a more powerful signal in order to be transmitted over greater distance. RF output power can range from a few mW to MW, depend by application. RF amplifiers before were all made using vacuum tubes but modern RF amplifier nowadays uses solid state devices like MOSFET, TMOS-FET, Bipolar junction transistors, and IGBT to amplify RF signals.

This circuit features the Freescale AFT05MP075GNR1 RF power LDMOS transistor as its RF amplifier solid state device. With the use of some components and proper board layouting, Freescale was able to create a 70 watts RF power amplifier with a gain of 18.5dB. This circuit requires a 12.5Vdc power supply able to provide the maximum power this LDMOS transistor can give. In this circuit, AFT05MP075GNR1 was configured to amplify RF signal with a carrier frequency of 520MHz suitable for UHF band mobile radio applications.

The Freescale AFT05MP075GNR1 was designed for mobile two-way radio applications with frequencies ranging from 136 to 520 MHz. It can be configured as a narrowband or wideband RF power amplifier. The high gain, ruggedness and broadband performance of this device make it ideal for large-signal, common source amplifier applications in mobile radio equipment. It can operate exceptionally in a very wide temperature range, from -40 to +150 degree Celsius. Though this device handles wideband application, it can still give full power across the band.

Narrowband RF Power Amplifier (520MHz) – [Link]