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50 Threads found on edaboard.com: Opamp Power Dissipation
Hi, I would need some help in a power dissipation issue. I have a power opamp that works in a non-inverting topology. Here some data: - Single Supply = 12V - Output voltage = 6+3*sin(wt) V - Output current = 100*sin(wt + alfa) mA where: w = angular frequency t = time alfa = angle between current and (...)
Put a zero-volt voltage source in series with all the op-amp stages and then measure the currents through them. This will give you power per stage - by V*I (of course) and is more useful, than just finding the total power for the opamp.
It all depend on the specification that you are looking for. Most of the time the process we use to design a opamp will be the crucial point as it will limit the design parameters and the rest as others mentioned in the post.
Due the application of dc feedback, I think a typical differential stage opamp would serve the purpose. If the frequency of application is high, a cascode stage differential opamp would serve the purpose Rgds
I need a opamp with DC gain>80dB and Unity Gain frequency >100MHz. At first I try to design it with the class-A two-stage structure. but it is difficult to satifiy both the DC gain and phase margin. Who can give me some advice about how to design. such as, if class-A structure can meet the request, or which kind of structure is more suitable. and
u r not designing an opamp, it's a wideband amp. if inductors r allowed, it would be easy.
hi! is it good to use folded cascode opamp for the bandgap? bcoz it have more pair to match and more prone to mismatch and introduce input offset.
In a conventional two stage opamp operating in weak inversion for ultra low power dissipation, does all transistors operate in weak inversion OR only differential pair transistor and tail transistor operate in weak inversion. Plz, Need help! Thanking You.
I am using a fully differential opamp (THS4131) for driving a 24 bit differential input analog to digital converter(AD7766). But there are many problems in my design , the drift voltage between two outputs of THS4131 is not a constant value and will increase by elapsed time. after 2000 seconds the drift voltage will increase to 610uV that is 10bit
Suppose I am using an opamp as an amplifier with +12V as pos and _12 as neg supply. Consider supply current as 3mA at no load.How will i calculate the power dissipation. Next is the opamp configuration as precision rectifier with same supply and current. Will there be any change in power (...)
Hello, In my design I am using an LM321 opamp for outputting max 24V with a current of 22mA. The LM321 is protected against short-circuits but only when not exceeding the maximum power dissipation. Is there a way protect the opamp against exceeding the maximum power dissipation when (...)
hye guys, I'm builiding an amplifier circuit using resistors and opamp(LM741). I already got everything about it, but I'm also asked to waste as little power as possible. Is there any solution for this. It seems like a very stupid question. I'm new to designing analog circuit. Thanks in advance for any help.
Hi all.. what should we really consider in designing opamp in BGR? thanks
hi, all when designing the op in bandgap reference, how large the load capacitance should we consider? (generally) i have designed a two-stage opamp with following specs that meant to be used as an error amplifier in a buck converter: DC Gain: 78db Phase Margin: 85 degrees G.B.: 10MHz PSRR: 100db loading: 5pF compensation capacitor: 3
Hello to all I am new in this froum ! i have the course Analog integrated Cmos design (razavi book is the ref.) semester but i dont know what to do. i have a Desgin problem and i dont know were to begin or what to do ! please take a look to my project and help me in design . if you have any link that have design like this so i could find the way
you're right, but I have not the complete knowledge of opamp circuits, and I have a very little time to make this circuit works (I know it's not the correct way to do these kind of works..) I have thinked that maybe there was a problem of impedance matching from the output of the first stage and the input of the second. So, looking in the output
To achieve the highest gain bandwidth, which one is more reasonable, multistage(3 stage) or gain boosting with 2 stage?
I am considering this circuit design for a low-cost voltage regulator: 60515 The load resistance (R4) is expected to be about 2.5 ohms. I am considering 2N3055 since I have them on hand and they seem to be a suitable fit with regards to their power han
If you take fast opamp and slow it down you will get what you need - like Video opamp. The OPA355 = 0.02% IN ≈50ns Regards Moda
the gain is moderate so you can do this design with 2 stage opamp. Use Nulling resistor to do compensation using transistor in triode mode. If you want step by step example, go to and look at P Ellen's lecture notes. This project is very do-able and won't take you long to design. Layout is another game, it comes with practice. G
I have designed an two stage opamp with following performance supply: 1.8V open loop gain: 87.1dB unity gain frequency :35.3MHz Phase Margin: 64 Slew Rate:11V/us CMRR:84.6dB PSRR-:65.5dB PSRR+:95.4dB Is there any other test i have missed? By the way, the slew rate is quite low, how can i improved it?
Hi all, How can I convert 50Hz AC to a square wave so that I can feed it to a microcontroller? Will CD4093 work here? I will steps down the ac to 5volts then use a diode in series before hooking it to CD4093? Thanks 1) Use a step down transformer to step it down to say 5V AC at 50Hz. 2) Then use a 741 op-amp fr
For 1, I think we should also consider the power dissipation or other spec. I prefer biquad since you implemented filter in sc filter. For 2, I think discrete time domain will give you similar result with continous time domain, and the accurate response maybe need to be verified in transient . For 3,4 . I think it depends on ur opamp (...)
1V supply opamp is not difficult. The point is what kind of specification is required. For example, input common mode range, output range, output loading, bandwidth and application.
I think for real low noise performance. say 2uV (20-30kHz), maybe opamp shouldn'd be used.
If CMFB is not present, the common mode gain will increase and deviates the basic idea of DIfferential opamp. So inorder to control the common mode gain,we introduce as Voltage controlled voltage source circuit. This will maintain a constant DC level at the output. This value is actually half way between VDD and VSS. Common mode feedback will have
"PMOS body connected to drain..." why not connected to power or source? Hi can anybody share to me a CMOS opamp net list roughly meeting the following specifications. DC gain >75dB Unity-gain frequency > 150MHz Phase margin at unity-gain frequency > 65o Slew rate > 50V/μsec PMOS body connected to drain and
If you need a 20mA clean current source, why not build it with and opamp? Why do you need the switching regulator? Perhaps I do not fully understand the application. Can you be more specific? A good source of info for switching regulators are the websites of TI, National, Linear Tech, Maxim.
Hello guys , I'm student in swiss federal institute of technology in Zurich . I'm very grad tojoinin this forum with all of you . In this semester, I have a semester thesis : design a high speed sample and hold (SH) circuit. I use T 0.13um CMOS technology ... For the OTA, that is used in SH circuit, I have tested all topology telesopic cascod
For me it look like switching time (rising and falling) problem and driving two MOSFETS of one general purpose opamp is rather NOT good engineering achievment .. One option to slove this problem is to put drivers between opamp's output and MOSFETs' gates - separate for each MOSFET .. BTW: Do you need this opamp at all??? You can (...)
The gain, BW and o/p swing u refer is for opamp or integrator?? You need to know the specifications such as the power supply voltage rail, power dissipation for determine the opamp structure. :D
ok i agree on that..... but what about the power dissipation, GBW, offset voltage etc etc..... actually what are you designing this opamp for.....
compared to inverting amp both common source and common emitter are cheaper solutions but they suffer from nonlinearity due to channel width modulation and early effect... inverting amp using opamp doesn't suffer from nonlinearity but the power dissipation is more....
what opamp are u using.... the MOSFET doesnt need current drive to drive it... my guess is that the inverters are used for speed opamps are generally slow compared to inverters....
Hello everybody, I want to design sample and hold circuit using double sampling technique at 160MHz clock (320MS/s) and 70dB IMD. Here I choose the two-stage opamp, the schematics are here. (Two stage module and the double sampling). But slew rate and charge injection decrease the IMD sharply. I try to adjust the miller capacitance, but the effe
In this design, there is another opamp circuit which is the same design as this one and those two circuits are working together. A LM7805 convert the 12V DC to 5V for powering those opamps circuits. I didn?t connect any load with this circuit yet. I only supplied 12VDC to LM7805 and the power is 12V and 0.38A, so I (...)
Dear All, I need to design an output stage (third stage) for a two-stage compensated opamp. I have gone through some related papers and text. After reading them, I have built-up some interpretations: 1. The main design specifications whilst designing the o/p stage are a) output swing, b) power dissipation (or efficiency), c) linearity (or
If you intend to calculate the W/L values that will make your circuit work as you want, forget it. That's just impossible because you lack the exact equations and the math would be extremely difficult. If your designing an high speed opamp your transistor sizes should be as small as possible to keep a good bandwidth. Besides that, PMOS should al
I have a 6v 1.3A battery and I want an opamp that works with it. I want the opamp tp draw as much current as it can from the battery. My question is, which part of an opamp datasheet should i be looking at in order to meet my needs. I think i understand the the voltage part but i don't understand how you can tell how much current will be (...)
I suggest you use several stage of opamp to get 65dB at 500MHz
Sugestion : I = 1,4A R = 0,1R P = (0,1R)*(1,4A)^2 = 0,19 ~1/5W V = (0,1R)*(1,4A) = 0,14V Use an opamp to multiply that voltage to full-range magnitude of A/D : K = 5 / 0,14 ~ 35 K = 3,3 / 0,14 ~ 23 Hope this help +++ ---------- Post added at 10:45 ---------- Previous post w
Hi, I want to design a circuit which can detect current pulses and give static voltage in accordance with current passed. For example if a current pulse of 10ms duration passes through my circuit than I want my circuit to give voltage and hold it there. I have tried using sense circuits for dc power supply in which a sense resistor senses curre
Current delivered from op-amp output to load depends on voltage at the output, load resistance Rl, output resistance Ro and your series resistance Rs. Current through load can be determined from Ohm's law. In that case Io=Uo/(Rs+Ro+Rl). Considering that Ro is internal resistance of opamp which is integrated circuit, you cannot chamge it. So the onl
input voltage is 25 v,R sens is 0.1ohm (Rshunt) and the current i have measure is 3.5A. 1. Can you please help in finding the value for resistors. If 25V is also the supply voltage for the opamp, use Ra=Rb=Rc=Rd = 1..10kΩ , R1=R2=100kΩ , and R3=R4 depending on your required gain = R3/R1 = R4/R2 . Thei
Hello All, I have to design a CMOS opamp at 135 nm Technology......... I have the circuit diagrams and parameters at 180 nm . I have to simulate it on TANNER EDA. I have model file for 135nm : * MOSIS WAFER ACCEPTANCE TESTS *
A couple more thoughts..... I would use a 1 Ohm resistor instead of 5 Ohms for the current sensing, to reduce the voltage loss and power dissipation. IIRC, a 741's inputs can't go all the way down to the negative supply rail, so it's probably a good idea to use a different opamp, or change the biasing.
1. Connect resistor between sensor resistor (200 Om) and opamp input . 2. Input Op Amp must be pulled to Vcc and GND through Fast/Schottky diodes (in reverse bias). It restricts input voltage level on the range -0.7V and VCC+0.7V
The maximum supply current is 4.5mA per opamp. There are two opamps. The total supply is 30V. Then the dissipation with no load is 4.5mA x 30V x 2= 0.27W. The thermal resistance of the tiny surface-mount case is 190 degrees C per W so if the ambient is 30 degrees then the chip is at 81.3 degrees C which is warm but not too hot. A load makes (...)
DISAD: folded opamp has larger silicon consumption
... It should deliver as much power as possible to a 20 ohm load. Therefore, I am trying to make the output impedance as near to 20 ohm as possible. No, to achieve this, Rout ≪ 20Ω ! Thus, obviously I should use a common drain MOSFET. However, the problem is output impedance of a common drain mos