# Tag Info

1 vote

### Need help opamp or optocoupler?

If only level needs to be changed and no isolation is needed, you can just use a voltage divider (2x resistor). The signal is slow enough for that. You can also use opamp with gain lower then 1 to ...
• 424
1 vote

### Constant volatge at the output of LM311

There is something wrong with your circuit, it does not match the schematic you've provided- maybe the LM311 is something else or the connections are not what you think. For example, the output ...
• 407k

### Voltage Divider with multiple voltage sources

After such thorough analyses, let's see what we have analyzed anyway:-) Here is a slightly fresher perspective on this circuit known as an "op-amp inverting summer". Conceptual circuit From ...
• 17.5k

### Voltage Divider with multiple voltage sources

I don't want to analyse your wall of ascii-math, but I'll comment on one approach. simulate this circuit – Schematic created using CircuitLab As you pointed out, $V_Q = V_P = +5.285V$, and ...
• 39k

### Infinite output impedance in amplifier, instead of 0?

Let's treat the op-amp and its periphery as a "black box", leaving only the load resistor $R_L$ outside: simulate this circuit – Schematic created using CircuitLab The "black ...
• 39k
1 vote

### Strange asymmetric saturation with ADA4099

The problem lies in the input stage of that op-amp. When the input signal is below Vcc - 1.5 volts, the input bias current is quite low and decent but, when the input signal rises to above 1.5 volts ...
• 465k
1 vote
Accepted

### Strange asymmetric saturation with ADA4099

These "over the top" devices draw significant current when you have a high enough input CM voltage to operate in that mode. The relevant datasheet section is on Page 21: OVER-THE-TOP ...
• 407k

### Infinite output impedance in amplifier, instead of 0?

Short answer The circuit presented by OP is a constant current source (op-amp and current-setting resistor RI) that supplies a "floating" load RL. Through negative feedback, the voltage ...
• 17.5k

### What type of amplifier circuit do I need to drive a piezoelectric ultrasound transducer?

Since transducer data sheets don't give many details of equivalent motional reactances and motional resistance, exact circuit values are not possible. Here's an idea for a very simple driver that uses ...
• 26.7k

### What type of amplifier circuit do I need to drive a piezoelectric ultrasound transducer?

You need to list specifications of what you are trying to accomplish. What is the purpose of your device? What is the duty cycle? Is it continuous or pulse? What sort of fidelity do you need? Is ...
• 10.3k

### TL072CP non inverting circuit doesn't amplify

I am using TL072CP Excellent. You got two op-amps, one can be used to buffer the input signal with a fixed gain and high(ish) input impedance, and then another to add variable gain. The circuit below ...
Accepted

### TL072CP non inverting circuit doesn't amplify

if someone could point out some stuff that are wrong with my circuit it would be of great help The first thing to point out is that your circuit will have an input impedance of 1 kΩ due to the ...
• 465k

### Audio Codec Input/Output Channel Stages

Input channel(s): The negative DC offset (R2/7/4) is dispensable. Use instead a DC blocking capacitor at the output of the op amp. You are attenuating twice by 5:1. The input resistive divider (R8/2) ...
• 661

### How to simulate for the Gain of opamp Bridge Differential Amplifier?

First, you calculate Vp using voltage division. This is accurate because the input impedance of the noninverting op amp input is relatively high. Next, because our "standard" op amp ...
• 30.1k
Accepted

### How to simulate for the Gain of opamp Bridge Differential Amplifier?

You can't use Vp-Vn ... because then you have the gain of the opamp (function also of frequency, perhaps 100k to 1 000 k ...). You should search the "gain" (transfer function) versus the ...
• 14.5k

### Infinite output impedance in amplifier, instead of 0?

Isn't the output impedance always 0 in an ideal op amp? The ideal op amp itself has zero output impedance, yes. But the output impedance of the amplifier you build with it can be anything but zero, ...
• 36k

### Infinite output impedance in amplifier, instead of 0?

When they say "output impedance of the amplifier" they mean output impedance of the closed loop amplifier. The circuit represented by the symbol below is an op amp, which you typically put ...
• 1,360

### Infinite output impedance in amplifier, instead of 0?

The output impedance of a two port network can be found by replacing the load resistor by a current source with known current $I_\text{TEST}$, calculating the voltage drop across it, and dividing ...
• 4,145

### Infinite output impedance in amplifier, instead of 0?

You are correct, the output impedance of an ideal op-amp is zero. However, the output impedance of the whole op-amp circuit that drives the load resistance Rload is not zero. You can think that the ...
• 159k

### Infinite output impedance in amplifier, instead of 0?

This opamp is being used as a transconductance amplifier, so it doesn't work the way you normally think of an opamp working. Assume $V_{in}$ is a fixed voltage 500 mV, the opamp wants to make both ...
• 25.1k
Accepted

### How are opamp node voltages being set in the following circuit and what is the use of the diode configuration?

So the first thing that stands out is that none of these configurations are proper usage of the guard voltage circuit. The guard trace should not be electrically connected to anything. For your stated ...
• 19.1k

### Is it correct to apply KVL through the 2 inputs of an op amp?

Short answer The circuit presented by OP is a constant current source that supplies a "floating" load and a current-setting resistor R in series. The voltage across the resistor is formed as ...
• 17.5k
1 vote

### Is it correct to apply KVL through the 2 inputs of an op amp?

are we allowed to apply KVL by jumping between wires? Yes of course. At every element along the KVL path, we jump from the wire connected to one terminal to the wire connected the other terminal. The ...
• 17k

### Is it correct to apply KVL through the 2 inputs of an op amp?

It's not KVL that makes the voltages across each pair of differential inputs zero, it's an effect of negative feedback and extremely high gain. It's also an approximation only and is invalid if the op-...
• 407k

### Is it correct to apply KVL through the 2 inputs of an op amp?

Negative feedback causes the op-amp to adjust its output potential to whatever is necessary to equalise its two input potentials. That's the principle behind the "virtual ground" you read ...
• 39k
1 vote

### How are opamp node voltages being set in the following circuit and what is the use of the diode configuration?

You would never run this circuit with a voltage source at V4. But if you do, look at the following explanation and internal op amp schematic from the data sheet: The guard buffer amplifier supplies ...
• 11.6k

### Operating principles of a sawtooth wave generator bootstrap circuit

This will definitely not work. How a negative feedback circuit with an op amp will provide and oscillation? I have search and this is is the only one source presenting this circuit. C2 cannot charge ...
Accepted

### Issues with ICL7660 ICs from eBay - Overheating and Failure

It's possible they are bad. Your photo shows an ICL7660S which is a different part (some improved characteristics, including a 12V rating) from the ICL7660 and ICL7660A. The logo and markings are ...
• 407k

### Issues with ICL7660 ICs from eBay - Overheating and Failure

There are improved versions of the xxx7660, for instance the ICL7660A from Renesas has a max supply voltage of 12 V and 45 mA output capability. The xxx7662 has higher voltage, up to 20 V, and ...
• 25.1k
1 vote

### Issues with ICL7660 ICs from eBay - Overheating and Failure

Since you bought from ebay, it's most likely either fake parts or parts which didn't pass testing. Throw them out and buy from any reputable supplier.
• 93
1 vote
Accepted

### What is the maximum dBu I can send into a microphone input in this schematic?

The op-amp is powered from 5V and has rail-to-rail output, guaranteed to be 4Vpp. We can assume ideal 5Vpp for simplicity. It is an inverting configuration, with gain of 20.6, which means the op-amp ...
• 159k
1 vote

### What is the maximum dBu I can send into a microphone input in this schematic?

The circuit has external input overvoltage clipping diodes, but we need to see more of the schematic to evaluate them in this circuit. Here is something to consider . . . The opamp circuit is ...
• 21.4k
Accepted

### Part name of this IC - "LLA#537"

Without knowing any more than what is in the post, like dimensions and surrounding circuitry; It's likely to be an Analog Devices ADP3334ACPZ, High Accuracy, Low IQ, anyCAP® Adjustable Low Dropout ...
• 1,424
Accepted

• 1,148

### Opamp inverting and non inverting issue

The Non inverting amplifier is overdriven, because its amplification A=2. Remove R4, so it will work as a buffer.
• 319
Accepted

### Opamp inverting and non inverting issue

U1.1 ( non inverting) has gain of 2, not 1. Remove R4 (make it infinite ♾️). Be careful: confirm that U1.1 is unity-gain stable for non-inverting gain of +1.
• 5,397

### About the vout of a different opamp circuit

I find the Vout value as -13V in the simulation, but I couldn't find it in the formula on paper. How can we find the Vout value? You have your op-amp connected as a comparator. This means that the ...
• 465k
Accepted

### port 7 and port 4 in the opamp that I can't make sense of

Pin 4 and pin 7 is power to the opamp. Without them it dont work.
• 159

### Related to the opamp question solution (a point I don't understand in the difference amplifier)

Trying to read between the lines, I think you are wondering how $\left(1+\frac{R_{13}}{R_{14}}\right)$ gets removed from the $V_x$ term in the equation. Perhaps the confusion so far is that you ...
• 11.2k

### Related to the opamp question solution (a point I don't understand in the difference amplifier)

Your question is not very precise. I can only guess, what you want. The opamp circuit you have drawn delivers: Vo = ky * Vy - kx * Vx Would you like to know how to ...
• 265
1 vote

### What is the purpose of the BJT in this circuit?

There are many good answers already, but I think one key point is missing: an external BJT is used because it has better heat dissipation and power handling. The purpose of the Zener voltage reference ...
• 1,360

### How would one calculate the transconductance of the FETs in this circuit?

The two formulas you show are correct. But you can't compute $g_m$ without knowing $V_{\text{GS}}$. And you need the DC operating point to tell you that value. That means you must work out the DC ...
• 11.2k
Accepted

### Solving complex opamp circuits

I've grabbed up the part you seem to be asking about and labeled an additional node. I'll be using SageMath/SymPy for the symbolic KCL analysis. It flows about like this: ...
• 11.2k

### What is the purpose of the BJT in this circuit?

The external transistor boosts the output current capability of the regulator. Without it, the current is limited by what the op-amp can deliver. Put simply, the Q1 NPN is a high-current voltage ...
• 55k

### Solving complex opamp circuits

It's called an MFB band-pass filter and is well-known in the industry. Here are a few references that get you started on what it's all about. Ref 1 from ESP Ref 2 from MT-218 Ref 3 from eCircuit I'm ...
• 465k

### What is the purpose of the BJT in this circuit?

Diode Z1 is producing a fixed potential, which for argument's sake, let's call $V_{REF}=+3V$. This will be used as a reference to control the output potential $V_{OUT}$. You might use only the op-...
• 39k

### What is the purpose of the BJT in this circuit?

Hmm. Okay. Let's redraw the schematic. Perhaps that will help you think about it: simulate this circuit – Schematic created using CircuitLab That should get you started. Just think about each ...
• 11.2k
1 vote

### How to gemerate a square wave circuit with lower level at 20V and higher level at 40V with several DC power supplies

You can use a hit and hold circuit, these work for high current load circuits with solenoids: Source: How do I use a hit and hold circuit with a solenoid? You need to specify the correct diode that ...
• 84.8k

### What is the purpose of the BJT in this circuit?

Suggestion Since this is homework, you will have to make an effort to understand this famous circuit solution. Okay, let's do it this way: I have broken down the sterile university schematic into ...
• 17.5k
1 vote
Accepted

### How to Properly Select Resistors and Capacitors for a Voltage Reference Circuit with BJTs

To build a voltage reference that depends on BJTs without feedback, diodes and potentiometers is not a good idea. This will not offer good voltage stability. You can select R6 and R7 based on the BJT ...
• 7,653

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