# power amplifier

1. ### gate current in a HEMT

Hello, I'm trying to understand the use of a HEMT as a power amplifier. I want to design a driver for a power amplifier and so I need to deliver enough current to charge the gate capacitance. I wanted to know if there is any other current I should take into consideration. For instance, the...
2. ### Small pull-down resistor for mosfet (fast switching, high capacitance)

Hi readers, When I used this IRF 3205 which has high capacitance between the Gate-Source of the mosfet, whenever I add a lower pull-down resistor, the switching becomes faster and faster (visible nice square wave). For my case, for IRF 3205 to fast switching at 20kHz (nice square wave), it would...
3. ### Optocoupler for high frequency

Dear Readers, I got this PS2501 optocoupler datasheet at here. In the image shown, the rise time and fall time is microseconds and I am afraid it's not suited for my needs as it will produce some switching losses in H-bridge circuit running at 100kHz minimum. Are there any very-high speed...
4. ### Maintain constant voltage across a variable load (op-amp)

Hi readers :), Vin is fed with the PWM signal coming from an op-amp to be amplified and fed into the load R1 (1 Ohms). The purpose I design this is I want the voltage source to be a constant 5V which is independent of the load (1 Ohms or 100 Ohms). So basically, this circuit has an op-amp which...
5. ### Regulate voltage using op amp

Hi readers, I am doing an Op Amp voltage regulation of voltage drop across load. As you can see from diagram, I have a fluctuating_Vin (0V to 50V) and I want the voltage drop at load (100 Ohms) to be the same (14V) at all times no matter whether input voltage is 20V or 30V or 50V? Note: I...
6. ### Amplify Flip Flop signal from NE 555 timer using transistors

Above is the graph across R7 (Load). Hi readers, Flip Flop with Ne555 timer means turning on an led and another one off, as shown in picture, and this alternate on and off pattern continues. This video can be found at Click Here . I have succeeded in amplifying one of the 2 signal as shown in...
7. ### How Power Supply Limit its Current Output ?

To view my We_bench power supply schematic Click here In the picture above, how does the power supply limit its max current and it has been fascinating for me to figure out how. Does anyone have a clue on this? I just know that the capacitor and diode help to rectify the AC output of...
8. ### Charging circuit modifications

Hi. above is a charging cut-off circuit. As you can see in my demo. when voltage source is 5V, the load (R9) has 5W power. When voltage drops to 4V, the load (R9) has 0 W (cut off). However, my lithium ion charging pin for my battery is 4.26V. Thus, when battery fully charged at 4.2V, the...
9. ### How do I not pass current with 0V input? is it possible to change the input voltage range?

Hello everybody! I have two questions. I have this circuit where I want to vary the input voltage (V1) between 0V and 5V to supply power to R2. Is it possible to make the circuit not supply a power (0W) to resistor R2 when my voltage V1 is 0V? When I do the simulation with 0V in V1 there is...
10. ### Oscillations on output of loaded LM675 for all positive voltages.

Hello, I'm trying to use an LM675 power op-amp IC as an output buffer for a signal generator. For stability, I've configured this IC as a non-inverting amplifier with a gain of 11 as per the circuit diagram below. As also recommended in the datasheet, I routed separate ground returns for the...
11. ### Tips for bipolar power supply

Hello, I need to design a linear regulated supply to power an dac output stage based on op amp. It must be a negative + ground + positive one. The problem I encounter is that I don't know wich topology to select between the first and second arrangement. I suppose that the first one induce a...
12. ### Maximum input voltage a diode can handle

Dear Team, May I know how to find the maximum input voltage a didode can handle.I checked many datasheets no info about this. Can I apply any voltage greater than it's forward voltage. Regards HARI
13. ### Audio amplifier

Hello, I have decided to build my own loud speaker from scratch. That means tha I will be building my own power amplifier. Now I want it to go as loud as it can so about 500W RMS should do it. I want to know are there any sites with schematis of such amplifier and I want a qulity one not...
14. ### 3.3v PWM to 10V to drive Power MOSFETS with Low Rds on?

Hello, I am designing and developing a low voltage Battery management system . i have designed whole circuit but in one small thing i am stuck. kindly help me answering it. Battery Pack specifications: 36 V 2.5 AH 10s battery pack. maximum voltage : 42 v Minimum voltage : 30v Power rail...
15. ### Darlington transistor POWER AMPLIFYING

Hi all, I just couldn't find the answer on web so I had to ask you guys. Based on my understanding, input power is ideally equal to the output power of a circuit unless it is dissipated to heat. So I was looking at the ULN2003 Darlington controlling a 28byj-48 stepper motor using an Arduino...
16. ### Power Amplifier repair

How difficult is to repair a Power amplifier in stereo receiver? The receiver model is shown in the link below. It's not an actual item I want to repair, but it same model as mine, so can be useful for information purposes: Stereo Receiver undercover How reliable is a board-level repair of such...