# Tag Info

12

In outline, it depends on the signal source, i.e. the type of microphone. There are some very low noise vacuum tubes. There are some low noise IC amplifiers, but not many. There are also discrete semiconductors, both bi-polar and JFET, and these are often the best choice for an input stage, possibly using an IC for the later gain and output stages. Among ...

7

The spectrum of interest is important : some otherwise very good amplifying devices have extra high noise at frequencies below 10Hz. Two options are worth considering : the first is bipolar transistors to provide useful gain before an opamp second stage. Why not go straight to an opamp? They are pretty noisy, very few have input noise voltage below 1 nV/...

6

The "maximum power transferred to the load" in you example doesn't refer to $R_L$ at all. In fact, most of the power delivered to $R_L$ has not been transferred to it, but rather added by the power supply of the amplifier. Actually, the load seen by the antenna is the input impedance of the amplifier, $R_{in}$ So, why it's so important to maximise the ...

5

FET input amps don't suffer from the same noise sources as resistors, which is how they can still have <100nVpp noise with input resistances in the teraohm range. Analog devices makes a "32" bit ADC w/preamp with input noise of <100nVpp, you could average out many samples to try to improve the noise floor (5sps for an hour should give you a couple ...

5

If the guitar pick-up were all that were in a guitar body then it would make sense to wire it differentially back to the differential input amplifier. That's where the story ends because to make the volume pot(s), tone pot(s) and pup-switching balanced needs much more complication. So, what about a standard guitar feeding a balanced input? No big benefit. ...

5

You can solve it as follows: Assuming a stable circuit in the Laplace domain we have Vn = Vp = GND. $$I_D - I_{CD} + I_{Rf} + I_{CF} + I_n = 0\\ I_{Rf}=\frac{V_{o2}-V_n}{R_f}\\ I_{Cf}=\frac{V_{o}-V_n}{\frac{1}{sC_f}}\\ V_{o2}=\frac{Z_L}{Z_L+R_{Fi}}Vo\\ Z_L=\frac{1}{sC_{Fi}}//R_f//R_L$$ where Vo2 is the output after RFilter and ZL is the load impedance ...

5

The OP277PA is an earlier version of the OPA277 precision opamp (Datasheet) If you scroll down to the orderable information you will find this the orderable part number for the device in a plastic DIP package. The final A refers to the die revision.

4

Beginner electronics. Searching the internet is your friend. There are so many web sites for beginning electronics. One place to go : http://www.hobbyprojects.com/ Click this for another site With amplifiers, the word GAIN is used to describe how much more the output signal is compared to the input signal. You could search for "amplifier gain ...

4

Power rails are connected to a +-15 V power supply, inputs of the first stage are connected to a function generator, with two channels, which inputs 2 180° out of phase sinusoidal signals and output is connected to an oscilloscope. It's quite possible that the function generator outputs are floating with respect to 0 volts on your power supply. You ...

3

A 24 volt supply with a single push pull output stage can, at absolute best, deliver an undistorted sinewave of 18 watts to a 4 ohm load. If you used two such push pull stages in a bridge you can achieve 72 watts. So, you need to be looking for a design that is based around what I've described above. This site isn't a free design service so I suggest you ...

3

I think this is a case of just confusingly worded Wikipedia articles. That passage would seem to suggest that if you ever have two noise temperatures then you can just add them together. As you've aptly explained, that doesn't make any sense. Rather, $T_{sys}$ is a figure of merit that's calculated by measuring the noise added by some component. The input ...

3

It's not obvious at all to me that 'a few' nV/sqrt Hz noise swamps your signal as you have said nothing about bandwidth. If your bandwidth is very low then there may not be a problem. Note that it is bandwidth not maximum frequency. Note that the quoted nV/sqrt Hz noise is above the 1/f corner frequency and if your frequency is low then you may have ...

3

If cost isn't an issue, then multiple LDOs can improve their heatsinking, by spreading out the dissipation. You may need to isolate stages for RF stability reasons. Don't think that separate LDOs give you much in the way of extra isolation at RF and microwave frequencies. It's series impedance, either small resistors, or better yet, ferrite beads between ...

3

The reason you need to match in this way is because you need to get the most power you can to the amplifier input itself. The electromagnetic signal traveling from your antenna to your first major impedance interface (your amplifier) will reflect a significant amount of power if they are not matched. If you suggest to make $Z_{in}$ bigger than $Z_a$, ...

3

The sensor requires a power supply with an output voltage anywhere between $\pm$ 6 volts and $\pm$ 15 volts, and the sensor will draw 10 milliamperes from the supply if it's a $\pm$ 6 volt supply. The data sheet doesn't specify the current needed by the sensor at other input voltage levels. The type of power supply will probably depend on what the ...

3

Typically pseudo-differential inputs have an asymmetrical input impedance- much lower for the 'low end' of the input. In this case, it only allows 300mV of common mode voltage. I didn't read the manual fully, but some instruments have 50 ohms relative to ground, which is high enough to prevent serious interference from ground loops. Of course a fully ...

3

This is undoubtedly all to do with the quality of the charger, as well, possibly your hands. You see, what a cheap 5V supply does (which is 99.9999999% of all USB chargers), is make a "floating-ish" voltage, which has only a very weak relevance to power earth. If at all. If it is a simple 2 prong adapter it may even relate the signal to one of those prongs ...

3

That board uses an INA-02186 device, which is not a bipolar transistor but a complete MMIC gain block encapsulated in a typical transistor package. This "performance figure" comes from a random ebay seller (to whom, by the way, I'm not related in any way): which, as you can see, is nothing but a snapshop from the INA-02186 datasheet: The INA-02186 is pre-...

3

Whether something is usable as a power amplifier depends on how much output power it can provide, and how much you need in your application. Look at the P1dB metric in the datasheet for each amplifier. This tells you how much output power it can provide while just beginning to enter compression. (You can squeeze another dB or two out of it by driving it ...

3

Here's a schematic of a typical CMOS mixer circuit: It's the classical "Gilbert" mixer. Although not clear from this picture, the bottom NMOS is just for biasing, you can view it as a DC current source. That makes the bottom half of this circuit identical to a standard differential pair. The inputs of this differential pair are connected to the outputs of ...

2

There are fundamentally two ways to increase the range of a wireless link: increase transmit power improve receiver sensitivity With a bidirectional protocol such as you have described, then a problem with either the transmitter or receiver would cause the link to fail. To diagnose a range problem on a link it is common to run some type of bluetooth ...

2

Implementing an approximation of an ideal exponential time-variable gain (TVG) amplifier is certainly a viable approach in ranging applications. The fall-off of response pulse (or chirp) with time is both enormous and predictable and can be thus profitably compensated for. Polaroid's ultrasonic ranging system (marketed in the mid-1970s, and used for such ...

2

You can start by looking at the noise spectrum of the LDO and the PSRR (power supply rejection ratio) of the op-amp over that spectrum. It's not unusual to add some passive filtering on the supplies (R+C or ferrite bead + C) for sensitive parts or a capacitance multiplier so even a relatively noisy source may not be an issue. The IC makers would like to sell ...

2

Resistors drop in noise proportional to the square root of temperature, so at 4.2K a resistor will have about 1/8 the noise as at 300K. Bipolar parts usually stop working entirely. Some GaAsFets apparently work okay, MOSFETs can work okay. The noise reduction will depend on the source of the noise. If it's white noise based on resistance it will ...

2

It depends on the crystalline structure of the epitaxial wafer and junction geometry and square of the current needed for bias in both conductor and dielectric. Flicker Noise is random pink noise usually measured <100Hz in $A^2/Hz$ as 1/f noise, but contributes to phase noise in RF. GaAs can be much better or worse than Si. carbon resistors are worse ...

2

If you are willing to calibrate each unit and then run it over a controlled temperature range, what you want should be doable. The biggest issue is no the gain error, but maintaining good signal to noise ratio. "Resonant capacitor" makes no sense, but resonance can be useful if the bandwidth of your signal is known and limited. This is usually the case ...

2

At least for now, just add a small amplifier after the one you already have. A gain of 20, with maybe a volume control in front of it should give you the range you need with some margin. You can rig up a little amplifier like that with something like a TL072 opamp and ±12 V supply. Once you have your system working, and therefore know what you ...

2

1) what are the challenges in designing amplifiers for high frequencies? Lets split that question into 2 parts ------narrowband design A narrowband design, with low phasenoise Local Oscillator, might have 100Hz bandwidth; NASA communicates with some satellites at such low bandwidths (low data rates); in a 50_ohm system at room temperature the noise floor ...

2

What are the challenges in designing Amplifiers with high frequencies? This depends on what you consider high. The challenging thing is always shifting. Where it used to impressive to get a few GHz out of standard CMOS, currently people are working CMOS circuits well into the millimeter wave spectrum - Oscillators at 500 GHz or higher, 200 GHz ...

2

The mixer is driven by a Local Oscillator. The level is (say +7dBm). It is never -65dBm. The RF being switched is -65dBm. It doesn't do anything - just goes through the mixer switches. In the basic and best type, a mixer is switches. Think relays. The local oscillator energises the coil and must be 12V. The RF goes through the contacts and can be any tiny ...

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