Electrical Engineering Stack Exchange
Electrical Engineering Stack Exchange

Questions tagged [low-noise-amplifier]

90 questions
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Amplifying a nV signal across a small resistance

I am interested in the feasibility of amplifying/measuring a nV level (or otherwise assumed very small) signal across a small resistance. The SNR of this signal isn't so bad in itself because of the very small thermal noise, due to the small value…
Orhym
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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 approach and it is still in development at the…
Rata
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How to reduce an audio system noise in a way which is similar to a human touching one of the system's components?

I have a somewhat weird question (hopefully not too weird). I work with an audio system. It includes a wave generator, a (33500B series Keysight) wave generator, an amplifier (2003 op-amp based circuit, will be replaced with LM1875 circuit in the…
user135172
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How to design wide band amplifiers?

I've been designing microwave power amplifiers and LNAs for school, I design in microstrip and my matching networks usually consist of stub/line sections or similar arrangements, I have also designed more sophisticated networks for wider bandwidths,…
S.s.
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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 white noise to my ears. Increasing C13 to 100 uF…
roc1
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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 very close to the nominal 50ohm). The 40db Gain is…
makkiato
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Antenna preamplifier design for ELF Schumann resonances receiver

I'm interested in listening to extremely low frequency band below 100Hz, where the famous Schumann resonances reside. I will use a large T shape antenna together with a very low noise, very high impedance preamplifier. This is my current draft of…
Matej Gomboc
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Microphone Amplification

I am working on a project using a microphone/microcontroller combination to detect if a clap has occurred. Thus far, I am using the Electret Microphone Amplifier - MAX4466 with Adjustable Gain from Adafruit, which uses a CMA-4544PF-W Elecret…
Zearia
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Electrochemical Measurements Using Lock-In amplifier

I'm trying to measure small electrochemical signals using a trans-impedance amplifier fed into a lock-in amplifier. I have an electrochemical cell that poses a very high impedance (100s of MegaOhms) that I feed a triangle wave into (5V P-P) the…
zzlmes
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Impedance matching vs. voltage gain

So I have an ultrasound system operating in the 1-10MHz range: Pulser -> Tuning circuit -> Transducer -> Tuning circuit -> Voltage amplifier The goal is, I'm trying to optimize the tuning circuits to obtain maximum signal at the voltage amplifier,…
user137089
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Why do we care about matching the input impedance of receiving RF amps?

Lets say we have a receiving antenna that intercepts a certain amount of power \$P_r\$ = \$SA_r\$, where \$S\$ is the power flow density of the incoming EM wave, and \$A_r\$ the effective area of the antenna. This power, \$P_r\$, is also called the…
Troels Folke
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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: (nV/√Hz) ⋅ √(bandwidth) = μVrms If I plug the numbers in…
KJ7LNW
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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 on these pictures: The left part of the circuit…
NNN123
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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
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What type of transistor generally has the lowest flicker noise?

How do BJT vs JFET vs HBT compare in terms of \$1/f\$ noise amplitude and corner freqency? I know these transistor types are very different, used for different frequencies and powers, and each have many different variations all with different…
wav scientist
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