Tagged Questions

1
vote
2answers
97 views

Circuit analysis of mono audio preamp (K1803 Velleman)

For a school project I have a question about the first part of the circuit below (amplifies at 20*log(220k/2.2k)=40dB). I know that U2A is the amplifying part of the circuit. The problem is U1A and ...
1
vote
2answers
98 views

Tips for adding voltage op amp to equipment

I have a source that creates a smooth sine wave in the range ±100mV at 1-15Hz. Due to distances I need to amplify the signal to at least ±5V, and I should also maintain the shape of the signal if ...
0
votes
1answer
222 views

Amplifying Low DC Voltage Consistantly

I'm looking to build an amplifier circuit to amplify a small DC voltage signal (between 0-15mV) to the range of 0-1.3V. I tried messing around with a standard non-inverting op-amp amplifier circuit ...
0
votes
1answer
38 views

Considering Loading in analysis and design

What are the conditions under which loading can or cannot be ignored? I would like to be able to design a circuit in segments and then connect these segments together to create a circuit that performs ...
1
vote
1answer
110 views

differencing op amp circuit

How would I implement an differencing op amp circuit that performs the operation 5*v1-2*v2 with the op amp power supply being 12vdc? I already tried the basic circuit but I got negative resistance. Is ...
2
votes
3answers
267 views

How do I calculate the gain of an op-amp summing amplifier?

So if I have a summing amplifier circuit like the one below: I know the Vin1, Vin2, and Vout value and the circuit is designed such that Vout = -(Vin1+2Vin2) but how do I calculate the gain? I know ...
3
votes
1answer
146 views

How do I use an LF355N JFET op amp to boost 2.8Vpp from function generator to 5V logic level

I have a Mini DSO DS203 portable oscilloscope. It can generate sine, triangle, and square waveforms with a peak to peak voltage difference of 2.8V. Desired frequency range is 0-200Hz. Duty cycle is ...
3
votes
2answers
208 views

Inverted Amplifier Circuit not working

In a nutshell: The below circuit is not working. The signal is distorted and is not amplified. I expect it to be amplified by R_1/R_2. The op-amp is a TL071. So my question is, how do I get this ...
8
votes
3answers
423 views

Audio Amplifier Op amp

I'm trying to design a circuit in which a microcontroller produces a signal and then using an amplifier drives an 8ohm speaker. I've so far used LM386, but it cannot go above 1W, which turned out to ...
5
votes
2answers
193 views

Input impedance of inverting amplifier clarification

Take a standard inverting amplifier: I'm unclear on what the input impedance is. At first I thought it was the equivalent resistance from the inverting input to the ground, which would be Rin || Rf, ...
2
votes
2answers
312 views

Humming and Transmission issues

First of all, I am going through designing all of this because I did not find a ready made circuitry for my purpose which is mentioned later. If you know a circuitry that is well tested and does what ...
3
votes
1answer
587 views

Capacitor values for non-Inverting op-amp circuit

I found the following schematic here and built it to test it . . . I think all the capacitors are there to just block DC, but how important are the capacitance values and how does one determine the ...
3
votes
3answers
237 views

Questions on some aspects of operational amplifiers

I am trying to learn the theory of operational amplifiers. I am using books like Millman, Halkias and Boylestead, but I found that these books do not actually tell the following aspects of those ...
2
votes
4answers
527 views

Simple op-amp differential amplifier

EDIT: Thanks everyone, I got it to work: Now if only I could accept multiple answers... . . . Is the output of this op-amp circuit linear in input voltage? The last equation \$A = ...
0
votes
0answers
167 views

Which op amp for microphone voltage follower?

I have been modifying a 4-channel digital field recorder to use specialist condenser microphones. I have got all the phantom power issues sorted and am able to make recordings. Channels 3 and 4 were ...
2
votes
1answer
431 views

Amplifying signal from CO2 Sensor

I am trying to amplify a MG811 CO2 sensor to a range readable by an ATMEGA2560 (0-5v). I have other analog sensors, so do not want to change ref voltage on Atmega. I have found a module that scales ...
6
votes
3answers
2k views

Scale 30-50mv signal to 0-5v range

I have a CO2 sensor that output signal values 30mV-50mV. I need to translate these voltages to 0-5V for my microcontroller with the highest resolution. I understand that I can amp the voltage using ...
4
votes
1answer
302 views

Why does an op-amp perform poorly with no load?

I have a THS4221 evaluation module (THS4221EVM, schematic on pg 1-3) powered with a bipolar +/-5V supply. My function generator (AtelierRobin F125) is generating a nice 1 MHz square wave, which I ...
-2
votes
1answer
179 views

Current to voltage converter proofing

Here's the circuit diagram for a current to voltage proofing and here is the proof for getting \$\dfrac{V_o}{i_s}\$ ...
9
votes
4answers
737 views

Signal Processing with Op Amps

I'm tasked to reproduce the following signal using only Op Amps (and resistors). I'm pretty sure I must add two signals, the square and triangular waveforms, it is just pretty hard to figure out ...
3
votes
3answers
404 views

Do two stage common emitter current amplifiers add or multiply?

So I've seen alot of explanations on two stage voltage amplifiers and how how their gains can be multiplied together. My question is when you are using a two stage common emitter amplifier for current ...
-2
votes
1answer
170 views

OP AMP amplifier [closed]

I am building a simple op amp amplifier circuit using IC LF351. I m using this circuit at very low voltages about 100mV. however the gain does not remain the same at this voltage. Like the theoretical ...
0
votes
2answers
277 views

Is feedback transfer function the same as the transfer function for the whole circuit?

I have a circuit very similar to the inverting band pass filter circuit here: I was asked a question about the circuit's feedback transfer function. Is this the same as the transfer function for the ...
2
votes
2answers
385 views

Why can't a feedback network use a capacitor? [duplicate]

Possible Duplicate: Basic Frequency Control Circuit In the following schematic, why can't R4 be taken away and the feedback network pass output feedback through C2 and R2?
-1
votes
1answer
163 views

Types of amplifier - what is the difference?

What is the difference between an open loop amplifier and a voltage follower (unity gain buffer)?
8
votes
6answers
3k views

Why is feedback required in op-amp circuits?

I understand that, in order for an op-amp to function correctly, a DC feedback loop from the output to either the inverting or the non-inverting input (depending on the external circuitry) is ...
3
votes
4answers
620 views

Basic Frequency Control Circuit

How does R4 prevent the output voltage drifting towards one of the supply rails to the op amp? I understand that R4 has to have a high resistance but I do not know why? Here is the schematic which is ...
4
votes
2answers
434 views

How do I use a clipping Zener at the input of an Opamp inverting amplifier?

I have a \$ V_{in} \$ signal for which I cannot guaranty that it would have an upper limit. I want to clip this input signal to a limit (e.g.; 8.2V) with a circuit like above. Is this circuit ...
1
vote
1answer
522 views

Simple and powerful audio amplifier around BA4558?

I have two BA4558 ICs from an old home stereo. I tested them with simple negative feedback circuit for each channel and with power supply of +/- 6V. The speakers I used are most likely with 8 ohm ...
6
votes
2answers
248 views

Why would a Diff Amp require both inputs to have a DC path to GND to work?

I'm looking at using a NI PXI-6255 DAQ card and I noticed in the manual it says "Both inputs of the (diff amp) require a DC path to ground in order for the (diff amp) to work." Is this a common ...
3
votes
2answers
148 views

Is there an amplifier such that the gain is equal to the ratio of two potential differences?

I have been toying with some alternatives to transistors in building logic gates. I am particularly interested in the device I tried to summarize in the title of this post. The chip would have 8 pins: ...
1
vote
3answers
300 views

Question about the output voltage of an op-amp. (ua741)

When i hook up my opamp to a 9 volt battery (like in the image below), i get 8 volts from the output pin. It gives the same reading when i attach both the inverting and non-inverting pins to the 9 ...
1
vote
2answers
772 views

Amplifying and filtering a very low frequency signal(Bandwidth of 4Hz)

Good night, everyone. I want to amplify and filter a signal that has a bandwidth of 3.5Hz and is of the order of 5 - 40 milliVolts. I plan to amplify the signal before filtering it so as to prevent ...
1
vote
2answers
660 views

Operation Amplifier with Transistor output

Is there a name for feedback amplifier topologies which include an opamp and transistor in the feed-forward path?. I need to design an amplifier with high bandwidth (almost 100 MHz) and high gain (50) ...
1
vote
1answer
560 views

Can I replace LM358N with NE5532N dual op amp?

In this circuit LM358N 1MHz 32V dual op amp is used (+12V and -12V). The question is, can I simply replace it with NE5532N 10MHz +-22V dual op amp for up to 8MHz DDS signal source? Basically, this ...
5
votes
3answers
2k views

Why the resistor in this op-amp circuit?

Here's a circuit diagram for a signal response test circuit from the spec sheet for a HA-5195 op amp and looks like a non-inverting amplifier circuit with a gain of 5, plus the 200Ω resistor between ...