# Solutions Search - Low Noise Amplifiers (<10nV/rtHz)

## Reference Filter Increases 32-Bit ADC SNR by 6dB

Sep 26th 2017

Design Note DN568: Introduction
Attaining optimal SNR performance from an ADC isn’t just a matter of providing a low noise signal to the ADC’s input. Providing a low noise reference voltage is just as important. While reference noise has no effect at zero-scale, at full-scale any noise on the reference will be visible ...

## Converting a Low Distortion Single-Ended Sine Source to Fully Differential

Sep 10th 2017

Customers looking for a way to evaluate ADCs with differential inputs will find themselves in need of a low distortion, low noise differential sine source. Single-ended sine sources can be obtained by building a simple Wien-bridge oscillator or by employing any of several readily available audio oscillators. Differential sine ...

## LTspice: Worst-Case Circuit Analysis with Minimal Simulations Runs

Jun 8th 2017

When designing a circuit in LTspice, you may wish to assess the impact of component tolerances. For example, the gain error introduced by non-ideal resistors in an op amp circuit. This article illustrates a method that reduces the number of simulations needed, and as a result speeds your time to results.
Varying a Parameter
LTSpice ...

## Low Power Op Amp: Low Power Filter, Headphone Driver Revisited

May 18th 2017

Design Note DN563: Introduction
A new family of op amps features industry leading speed versus supply current. The LTC6261/LTC6262/ LTC6263 family (single, dual, quad) provides 30MHz at a low 240μA supply current, with 400μV maximum offset voltage and rail-to-rail input and output. In combination with 1.8V to 5.25V supply, ...

## High Linearity, Low Noise LTC2387-18 Drivers for Sinusoidal Signals

Jan 10th 2017

Introduction
The LTC2387-18 is a high speed SAR (Successive Approximation Register) ADC suited for high linearity, low noise applications. This ADC is capable of sampling at up to 15Msps, which allows it to convert signals at frequencies of several MHz. It is well-suited to convert both pulsed and continuous signals in this ...

## LTC2387 Drivers Part II: Drivers for Imaging

Dec 8th 2016

A Driver for Imaging (short version)
The circuit shown below works great. You should try it.
This is intended for nominally 0-3V single ended or differential signals, from CCDs, CMOS image sensors, or other similar signal sources. As shown, SNR is 88 dB. With the AD8008, in place of U1, and a few other minor changes, it ...

## Hybrid Wide Dimming Ratio Linear LED Current Controller Using LT8614 & LT3083/LT6015

Oct 17th 2016

Many applications for LED illumination require wide dimming ratios. This can be accomplished simply via an adjustable current source as show below. The current source can be varied by a number of different means, and a large LED current range can be achieved. The primary problem with this technique is that the power dissipation ...

## Op Amp Precision Positive & Negative Clipper using LT6015/LT6016/LT6017

Oct 3rd 2016

It can be a challenge to match the voltage range of an analog signal to the input range of an analog to digital converter (ADC). Exceeding the ADC’s input range will give an incorrect reading, and if the input goes far enough beyond the power supply rails substrate currents can flow into the ADC which can cause latch up ...

## Single-Ended to Differential Driver Circuit for the LTC2387-18 SAR ADC

Sep 26th 2016

The LTC®2387-18 is a 15Msps, highly linear, low-noise SAR converter with differential inputs. The combination of excellent linearity and wide dynamic range makes this ADC ideal for high speed imaging and instrumentation applications. No-latency operation provides a unique solution for high speed control loop applications. ...

## LTC2387 Drivers Part III: Trans-Impedance Amplifier/Driver

Sep 8th 2016

This is unabashedly a classic case of what marketing calls “a solution looking for a problem”. It is an example of how the full SNR of the LTC2387 may be realized for a real world signal. Most signals originating in low level circuitry, in sensors, or in the real world, will require significant gain to develop 8Vp-p ...

## LTC6244 High Speed Peak Detector

Aug 1st 2016

Introduction
Peak detectors capture the extrema of the voltage signal at its input. A positive peak detector captures the most positive point of the input signal and a negative peak detector captures the most negative point of the input signal. Ideally the output of the peak detector circuit tracks or follows the input voltage ...

## How to Drive the LTC2387 (Part 1): Signal Applications to 5MHz that Require Low Inter-Modulation Distortion

May 13th 2016

The biggest challenge in driving a 15Msps, 18-bit ADC with an 8Vp-p input range is the lack of integrated amplifiers with adequate bandwidth, low noise, and the required output excursion. There are low-noise, high-BW amplifiers than can produce 2VPP. There are low speed amplifiers than can produce 8VPP. For low distortion beyond ...

## Low Power, Precision Op Amp Simplifies Driving of MUXed ADCs

Oct 2nd 2015

Design Note 1034: Introduction
The high speed op amps required to buffer a modern 16‑/18-bit analog-to-digital converter (ADC) typically dissipate as much power as the ADC itself, often with a maximum offset spec of about 1mV, well beyond that of the ADC. If multiple multichannel ADCs are required, the power dissipation can ...

## Injection-Lock a Wien-Bridge Oscillator

Sep 22nd 2015

I recently had the opportunity to investigate a new micropower 6-MHz LTC6255 op amp driving a 12-bit, 250k sample/sec LTC2361 ADC. I wanted to acquire the FFT of a pure sinusoid of about 5 kHz. The problem is that getting the FFT of a pure sinusoid requires, well, a pure sinusoid. Most programmable signal generators, however, ...

## Signal Conditioning for High Impedance Sensors

Sep 22nd 2015

Abstract
Dealing with high impedance sources and maintaining high impedance inputs without compromising reliability has its own set of challenges. This article offers qualitative and quantitative discussions of issues associated what high impedence circuits, what types of sensors are high impedance, and what devices are available ...

## Positive to Negative Converter with Variable Output Using LTC3630 and LT6015/LT6016

Sep 1st 2015

There was a window of time in the 1950s and early ’60s when negative voltage rails were commonplace, when germanium PNP transistors were prevalent—like those used in an old “transistor radio”, now worth a fortune on Ebay. Nowadays, NPN transistors are more prevalent, since they basically work ...

## Paralleling Amplifiers Improves Signal-to-Noise Performance

Jul 9th 2015

Dealing with low amplitude signals can be challenging. In order to differentiate between the low level signal and the noise contributed by surrounding circuitry, we typically use gain to amplify the signal above the noise floor. However, a standard amplifier configuration multiplies the input signal, the input noise, ...

## Sometimes You Need a Little Gain Part 2

Apr 28th 2015

Introduction
Part 1 of "Sometimes You Need a Little Gain" dealt with a pseudo-differential ADC driver with gains of one to ten. This time a fully differential ADC driver, again with gains of one to ten will be described. First a brief recap on the LTC2373-18 SAR ADC and a description of the LTC6237 op amp which will be ...

## Sometimes You Need a Little Gain - Part 1

Apr 9th 2015

Introduction
The LTC2373-18 is an 18-bit, 1Msps, 8-channel SAR ADC with an integrated high performance reference and programmable sequencer. The LTC2373-18 can be configured to accept both pseudo-differential (unipolar and bipolar) and fully differential input signals. For best performance, an op amp should ...

## Loop Gain and its Effect on Analog Control Systems

Jan 26th 2015

Abstract
This article brings together the ideas of open loop gain, closed loop gain, gain and phase margin, minimum gain stability and shows how these parameters are interrelated in a feedback system. It examines loop gain in terms of a theoretical control system as well as practical electronic circuits, including linear regulators.
Introduction
Bob ...

## Robust High Voltage Over-The-Top Op Amps Maintain High Input Impedance with Inputs Driven Apart or When Powered Down

Nov 5th 2014

Introduction
Linear Technology’s Over-The-Top op amps have an input stage topology that allows them to operate closed loop well above the positive supply rail. The inputs remain high impedance when split apart in voltage and also when shut down or with complete loss of power supply. They are indispensable in robust ...

## Locating Shorts on Power Planes of Multi-Layer PCBs

Aug 7th 2014

Occasionally multi-layer PCBs arrive with power to ground shorts that are difficult to locate. Usually the response to questions about finding these shorts is to just “Hook it up to a 12V battery and find out where it smokes.” While this may work, it’s usually not desirable since the board will probably be ...

## Driver for 14-Bit, 4.5Msps ADC Operates Over a Wide Gain Range

Apr 3rd 2014

Introduction
The LTC2314-14 is a 14-bit, 4.5Msps, serial output ADC with an integrated high performance reference. The single-ended input of the LTC2314-14 is easy to drive and in many instances does not require a buffer. A driver, such as the LT6236 op amp, may be required for a signal that is small or has high output impedance. ...

## LTspice: Stability of Op Amp Circuits

Nov 6th 2013

We all know that feedback circuits can oscillate. We may even know some tricks of how to fix it. But wouldn’t it be nice if our simulation tool could show us exactly what is happening, and why? This video illustrates how to use the .AC analysis to look at open loop gain and phase of operational amplifier feedback circuits ...