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Questions tagged [low-noise-amplifier]

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Automatic gain control and Tayloe detector

For a recent project, we need to build an RF IQ frontend to detect tones at 500kHz sent by a nearby transmitter. We want to use the Tayloe IQ detector followed by baseband ADC conversion to be able to ...
Joan Solà's user avatar
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1 answer
49 views

Filter for supply voltage of amplifiers

I need to design an ultra low noise amplifier in transimpedance architecture. This is the architecture I have chosen: In addition to the decoupling capacitors on the supply pin I have also added two ...
Andromeda's user avatar
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4 answers
89 views

Should I use a metallic enclosure for my low-noise circuit?

I am trying to design an ultra-low-noise pre-amplification stage for a MEMS. The amplification consists of a non-inverting amplifier specifically chosen to have less than 4 nV/sqrt(Hz) as input ...
jrad's user avatar
  • 3
1 vote
1 answer
64 views

Advice on using limiters for circuit protection in HF circuit [closed]

I am designing a receiver amplification circuit and I'd like some advice. We operate in the 10-20 MHz range, and in proper operation receive input signals on the order of -35 dBm. Our current RF chain ...
Theo's user avatar
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0 answers
37 views

Trying to make a WiFi Range Extender using Skyworks

I'm trying to design a WiFi range extender that can help increase the range of RF signals from an Intel M.2 8265NGW module. Similar to how these amplifiers from sunhans and others do. I initially ...
Mo Mizzi's user avatar
1 vote
1 answer
50 views

Calculate noise figure for LNA + SAW + RTLSDR

I'm trying to optimize the SNR of low-power RF pulses (from wildlife telemetry tags @166Mhz, unmodulated, a few DBs above noise floor) as they go into an RTLSDR. I have a number of questions about how ...
TvE's user avatar
  • 286
1 vote
1 answer
61 views

LNA operating in saturation

What happens to an LNA noise figure when operated in saturation? I understand that there will be gain and linearity issues, but what about its noise figure? What is the mechanism which will lead to ...
cesar's user avatar
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0 answers
74 views

Could DC-DC isolated power supply switching noise harm the input of an instrumentation preamplifier?

I am looking for a noiseless protection against 100ms pulse of 1kV of an input of ultralow noise instrumentation preamplifier (eight AD8428 connected in parallel, fixed gain of 2000) to measure very ...
NNN123's user avatar
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1 vote
2 answers
171 views

How to design an RF frontend for an FM receiver

I'm designing a RF receiver for FM Radio. I simulated the circuit in LTspice and got an output as shown below: This is OK, but I would like the gain to be 24 dB across the range of 88-108 MHz. The ...
TheButterMineCutter's user avatar
1 vote
2 answers
128 views

Using a low power reference voltage source to regulate higher power supplies

I want to put together (1) a cheap home breadboard reference current supply to calibrate and test 3 1/2 digit DMMs and (2) a low noise power supply to replace batteries in battery-powered audio ...
Sara's user avatar
  • 212
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1 answer
86 views

LNA drawing less current than expected

I'm trying to design a low-noise amplifier circuit for the 8-20 MHz range. The circuit will be used to amplify received signals from an antenna, while blocking signals when the antenna is transmitting....
Theo's user avatar
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2 votes
3 answers
1k views

Why do amplifiers have minimum frequencies?

RF amplifiers, both power amplifiers and low noise amplifiers, are rated with a minimum and maximum frequency. For example, the Analog Devices HMC517LC4 Low Noise Amplifier has a frequency range of ...
SRobertJames's user avatar
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1 vote
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68 views

What are the PCB design guidelines to achieve a noise floor of 0.1 mV? What are the significant measures to reduce the noise floor to 10 micro-V?

I am designing a photodiode (PD) readout circuit containing the PD, I-V op-amp, the amplifier's 2.5 V regulated supply, and associated resistors & capacitors. The op-amp's output will be connected ...
Vishnu's user avatar
  • 11
2 votes
1 answer
241 views

Noise Figure in LTSpice

I'm simulating an LNA from a paper. It's using HBT BiCMOS technology an one of the things the paper shows is the simulation of NF in range of 3GHz to 10GHz. I'm trying to replicate the simulation with ...
JOAQUÍN PIÑEIRO's user avatar
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0 answers
46 views

Is an output noise in the micro range any good?

I have designed the below circuit, as mentioned in the previous post the input is a 50mV RMS @ 50Hz signal, the bandwidth is 1kHz, and the output amplifies this by 20V/V. I have seen people do a ...
JoeyB's user avatar
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1 vote
1 answer
261 views

How do you use an RC filter on an LNA output to reduce unwanted noise?

We designed two low noise amplifiers, one at 144 MHz and another at 440 MHz using this LNA; each design is tuned for the particular band. We noticed amplification at 440 MHz is clean and crisp, but ...
KJ7LNW's user avatar
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1 vote
1 answer
295 views

Low Noise - High DC Accuracy Voltage Reference Buffer ? Composite Amplifier?

I want to built a low noise voltage reference buffer to drive an ADC and additional analog circuits. Main requirements: "Ultra"-Low Noise Best DC accuracy possible (mainly interested in ...
huababua's user avatar
  • 115
0 votes
1 answer
144 views

What kind of relay is used for high-power RF front-end applications?

My son and I are designing an RF frontend at 146MHz with a 300W amplifier on the TX side an an LNA on the RX side to be placed near an antenna feedpoint. The frontend will be inline to an existing ...
KJ7LNW's user avatar
  • 2,088
0 votes
1 answer
391 views

When should you use a gate driver, and how do you choose one?

I'm building an amp using the NXP MRF300AN 300W LDMOS RF power amplifier device and was originally planning to use a DAC to drive the gate bias until @Hearth mentioned that I should use a gate driver. ...
KJ7LNW's user avatar
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2 votes
1 answer
131 views

Does an LNA with a dedicated Vbias pin affect impedance matching?

I am optimizing an impedance match for an LNA in my target frequency range using a Touchstone s2p that Qorvo provides for the QPL9547 (datasheet). The Vbias pin is separate from the RF-in pin. I'm ...
KJ7LNW's user avatar
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0 votes
1 answer
215 views

Can an LNA noise figure be normalized to dBm to estimate the minimum detectable signal?

If a device claims a noise figure of 0.3 dB NF such as the Qorvo QPL9547, can you calculate the dBm value of a signal that is at the noise floor (ie, a barely detectable signal)? Otherwise stated: I ...
KJ7LNW's user avatar
  • 2,088
10 votes
7 answers
3k views

Transimpedance amplifier for very low currents

I am currently working on a project, which requires me to measure the very low currents (approximately in the range of 100 pA to 10 uA) from an electrochemical sensor. The sensor is kind of a new ...
Rata's user avatar
  • 111
3 votes
1 answer
401 views

Digitally tunable gain, low-noise instrumentation amplifier

I want to make a digitally-tunable gain (~1 to 1000x), low-noise instrumentation amplifier. There are integrated ones (e.g. AD8557) but the input noise is too high. My current plan is to use an ultra-...
Eric M.'s user avatar
  • 33
0 votes
2 answers
1k views

How does an Instrumentation Amplifier reduce DC offset?

While researching different current measurement methods, I came across a particularly interesting circuit which has a very high input impedance and apparently reduces the effects of the input offset ...
A.H.Z's user avatar
  • 633
0 votes
1 answer
191 views

I'm looking for an SMD diode in a (small) haystack, hearing aid repair [closed]

It works, but it buzzes through the earpiece if you turn up the volume much, I'd like to do some signal tracing, but first I'd like a schematic. I found one using 3 NPN transistors that might be close,...
Henry Dedrick's user avatar
0 votes
2 answers
2k views

Noise figure to voltage noise spectral density hand calculation

The RF LNA of interest is the PGA-105+ from mini-circuits. From only the gain and noise figure I calculated the voltage noise spectral density that would be present at the amplifier input. If anyone ...
Max W's user avatar
  • 83
1 vote
2 answers
271 views

How could I build an amplifier circuit that can take an input voltage of 0-0.7V and amplify to 0-32V, 1 ampere, that works for 100 MHz?

A little background first. I am trying to build a pretty dumb project where I try to take a VGA input and display it in a manner similar to a Nipkow disk. The high frequency RGB signals need to be ...
3eeeeeee512's user avatar
-1 votes
1 answer
298 views

Low noise electret microphone amplifier with automatic gain control

I am looking for a simple solution to design a low noise electret microphone preamplifier with automatic gain control (AGC.) Generally, I need to pick up the sound from a far distance, digitalize it ...
Jan Riha's user avatar
  • 137
4 votes
2 answers
1k views

Some LDO's specify noise in nV/Hz, others specify it in μV(rms). How do they equate?

The "low noise" LDO TI TPS7A20 specifies output noise as 7μV(rms) at 100kHz, whereas the Diodes AP2210 specifies output noise as 260nV/√Hz. This SE answer compares the two mathematically as: ...
KJ7LNW's user avatar
  • 2,088
0 votes
0 answers
67 views

What are the qualities that you look for in a 2nd stage LNA?

We are building a multi-stage LNA for a TR module we are building in the 144MHz and 440MHz range. The 1st stage LNA has to be the most sensitive---but what is important to consider when choosing a 2nd ...
KJ7LNW's user avatar
  • 2,088
0 votes
0 answers
114 views

How would you filter the DC input suitable for use to bias/power an LNA?

We are building a transmit/receive module for the 144MHz and 440MHz bands. As I understand, a good LNA can provide poor performance if the environment or the bias voltage is too noisy. What are the ...
KJ7LNW's user avatar
  • 2,088
1 vote
2 answers
206 views

CNY70 and LM358 amplifier circuit not behaving as expected

I have reproduced a circuit proposed by Nicholas Burnett in 2013: An improved noninvasive method for measuring heartbeat of intertidal animals please see Fig. 2 which looks as follows: The circuit ...
Marco Bobinger's user avatar
0 votes
3 answers
382 views

I need a pre-amplifier for my sound card with high gain without noise [closed]

I'm trying to make a pre-amplifier for my PC microphone with high gain and low noise. I tried a few circuits but they had a lot of noise and low gain. How can I make a preamplifier with high gain and ...
Macan's user avatar
  • 19
0 votes
0 answers
75 views

Additional gain with in-amp for nanovolt-scale pre-amp

Currently I'm designing a pre-amp for detecting nanovolt-scale(~100nV, <1kHz) signal for experiment. I need a final gain to be around ~100000. Since the magnitude of the signal is extremely small, ...
Chanwoo Ahn's user avatar
0 votes
0 answers
247 views

Photodetector and low noise amplifier acting as low pass filter

I need some basic advice for impedance matching: I have a photodetector (Det01CFC from Thorlabs, https://www.thorlabs.com/drawings/275cb418cdc2cf1f-A2E46103-D9C0-3581-4553E3D3CA93AD83/DET01CFC-Manual....
Sandro Camenzind's user avatar
1 vote
0 answers
50 views

Building a “if” statement circuit where i can control different light diodes

I want to design a circuit to react in different ways depending if a microphone picks up one frequency and in different way if it picks up the some other frequency. I want different lights to shine ...
Frans Myrberg's user avatar
0 votes
3 answers
162 views

Audio amplifier components

I want to understand the purpose of capacitors and variable resistor in the following audio amplifier circuit. Here is its datasheet. C118 at amplifier output pin. C424 between amplifier input and ...
scico111's user avatar
  • 907
0 votes
1 answer
93 views

How do you choose components for a gps antenna

I have to solder an active gps antenna on a pcb. But I don’t know how to choose components. In my case antenna will be used outdoor on a pet collar. First of all there are a lot of different ceramic ...
Denis Jelesniak's user avatar
2 votes
3 answers
5k views

How to build a low noise MIC preamp

I want to be able to talk on the microphone of my Headset A and send that signal out to the earphones of my Headset B. Something similar to what I show you on the image below. For that purpose, I ...
davidesp's user avatar
  • 123
1 vote
3 answers
160 views

Do parallel LNAs at 90-degrees to eachother reduce the noise floor more than side-by-side?

Wiring amplifiers in parallel in a summing configuration improves the signal to noise ratio because amplifier noise in each LNA is uncorrulated. However, external noise sources will still be a factor ...
KJ7LNW's user avatar
  • 2,088
0 votes
1 answer
433 views

How does wiring two LNAs in parallel affect charactaristic impedance?

It appears that wiring amplifiers in parallel improves the signal to noise ratio. I thought I would experiment with two SAV-541+ LNAs in parallel and see how they perform: How does wiring an LNA in ...
KJ7LNW's user avatar
  • 2,088
5 votes
3 answers
190 views

Mic amplifier noise

I build a mic amplifier for a standard hands free (Apple 4-pole jack). However, even without anything plugged into the jack there's audible noise at the output (MIC_IN in diagram). It sounds like ...
roc1's user avatar
  • 53
5 votes
1 answer
286 views

Understanding Noise Figure of LNA (HP 461A amplifier)

I have recently got a HP 461A linear amplifier (from the 60's) which works from 1Khz to 150Mhz. I have checked that: it's input gives a SWR <1.1 across all spectrum (i.e., the input impedance is ...
makkiato's user avatar
4 votes
2 answers
682 views

Ultra low noise charge sensitive preamplifier

I developing charge sensitive preamplifier for radiation detector. This is a very sensitive device, the smallest amount of noise can completely ruin the signal. The schematic and the PCB you can see ...
NNN123's user avatar
  • 103
0 votes
0 answers
137 views

12-15V to 9V power supply required to power audio equipment

I have a 12-0-12 transformer with output after filtering 15-16V. It's for audio equipment uses. I want to power a guitar pedal with 9V. I tried L7809 but it's making a whistling noise, so I tried ...
user254181's user avatar
1 vote
2 answers
411 views

Understanding the circuit diagrams for white noise generators

I'm a huge neophyte when it comes to electronics, and I'm trying to work out how to create a white noise generator for a project. I've been looking at some to base my examples off of. One of which is ...
sangstar's user avatar
  • 121
2 votes
1 answer
566 views

How to measure Johnson Noise precisely experimentally?

I want measure Johnson Noise across a resistor having certain over the certain range of frequency or bandwidth practically. I am starting from scratch, how can I build circuitry and instrumentation so ...
learner's user avatar
  • 201
5 votes
4 answers
3k views

In a Class-C power amplifier, what does the resistor in the base do?

Look at the picture, which shows a Class C power amplifier (source). What is the role of the resistance in the base of the transistor, and what happens if it's removed?
Alex L's user avatar
  • 302
0 votes
1 answer
160 views

Can a Unilateral Amplifier be Unstable?

When designing microwave amplifiers, stability is an important factor to consider. Stability is usually measured with the K factor. In a unilateral network, S_12 = 0, and this makes the K factor ...
Alex L's user avatar
  • 302
0 votes
1 answer
73 views

Selection of Frequency in Switching Regulator

The AD ADP5070 for feeding a low noise amplifier and a 24 bit ADC, can be regulated at two pin selectable frequencies: 1.2MHz or 2.4MHz, accepting an external oscillator in the range 1 MHz to 2.6MHz. ...
Brethlosze's user avatar
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