Continue to Site

Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

0 ~ 50 Volts, Low power Amplifier

Status
Not open for further replies.

ata90

Member level 5
Joined
Apr 13, 2009
Messages
89
Helped
1
Reputation
2
Reaction score
1
Trophy points
1,288
Activity points
1,945
How can we design a circuit which can amplify 0 ~ 10V to 0 ~ 50V correspondingly?
(Assume output current 20mA)
 

You may use a high voltage operational amplifier

https://www.ti.com/lit/ds/symlink/opa551.pdf
OPA445 - 90V supply with 15mA continuous output instead of 60V, 200mA.
OPA452 - 80V supply with 50mA continuous output instead of 60V, 200mA
OPA551/OPA552 -


https://www.analog.com/library/analogDialogue/archives/39-05/Web_Ch6_final_I.pdf

or use an output “booster” to achieve the needed voltage. Normally, this stage is placed within the feedback loop of the operational amplifier so that the low drift and stable gain characteristics of the amplifier are retained.

https://how-to.wikia.com/wiki/How_to_boost_the_output_voltage_swing_of_an_operational_amplifier
 

Very useful information.. Thank you mister_rf
OPA series are very expensive components. so that's better to design.
According these references, Bootstrap technique is offered. so we can not boost dc voltage. am I right?
is there a way to boost dc voltage in the range of 50V too? similar to what usual Op-Amps do in the range of 30V
 

What is the signal type , cable capacitance and load impedance?
Is this Analog or Digital?
DC or AC?

One can design a simple solution ONLY if the problem is well defined.

Personally I like using old Car Ignition Coils as audio signal boosters.. Ha ha ha Works well on 20mA

You can increase DC voltage for low power using a series of Doublers or Triplers... Diode Cap
ESR will add up on caps but 50V/20mA sounds like 2.5KΩ load.
You can use low cost 0.1uF Caps and choose impedance of Caps for your chosen clock rate with a low impedance high current Clock driver of 100mA or more to pump caps up. Make sure driver ESR is as low as Cap ESR or account for Time contants.
 
Last edited:

That's simple. input is a analog DC signal which I can change it in the range of 0 ~ 10V. now I want to boost it in the range of 0 ~ 50V rail to rail. assume output load is 15 mA.
 

You can use 10V to 50V using a 5stage DC multiplier with any kind of Totem pole low impedance current pump clock to drive the chain of CR-C-CR-C-CR-C at the appropriate frequency for the Caps you have chosen. Ceramic is adequate at these low currents.

If you want it regulated, use a 6 stage with an LDO. Since these are penny priced parts, it is only real-estate of PWB, but you can also choose a 98% efficient Boost DC-DC regulator for a few bucks ( no pun ) in small volume. Depends on what else is important.

Screen shot 2012-05-19 at 1.26.23 PM.PNG use common diodes rated for your application. Schottky will be lower loss than silicon. Ceramic 0.1 cap is ok < 2Ω @ 1MHz Choose cap and Freq, based on desired current and Z from nomograph in seconds.
Frequency - Reactance Nomograph.gif
SMD parts are small and cheap, but your design cost spec is not defined.

Also your intended Application is not mentioned !!!! Don't be slack next time and give all the details.
My crystal ball say you really want a constant current driver for a string of LED's < 50V, then there are custom LED DC-DC CC switchers avail now.. But's that's too easy.. ;) e.g. 1A 60V max rated CC or CV <$2 **broken link removed**
 
Last edited:

I would discuss the question of circuit power supply and amplifier design separately.

If you don't like special high voltage OPs, you can either refer to discrete transistor amplifiers, or a combination of transistors and standard OPs to increase the voltage accuracy. You didn't specify much except voltage range and 20 mA output current. You should define also bandwidth respectively slew rate and acceptable voltage error. Is an output without current sink capability sufficient.
 

Why would anyone want 50V analog at high impedance? 15mA for an analog signal?

hmmm
COMM Tx for Bats using quartz transducer and broadcast clicks with Beethoven?
 

Please see below image which shows ideal black box circuit. I just mean a circuit which can multiply input DC voltage by 5.
bandwidth and slew rate are parameters when we apply sinusoidal signals. here we just have variable input DC voltage. it means when I set input to 5V, it permanently stays on 5V. and I expect the output voltage be 25V.
assume acceptable error 5% or less.

Drawing1.png
 

What is in my mind is circuit below:
POWER.png

by varying potentiometer, output dc voltage of op amp is in the range of 0 ~ 10V. multiplying it by 5, we have voltage in the range of 0 ~ 50V. so output of Power transistor will be in the range of 0 ~ 48V.
 

  • OK this looks like homework...
  • You need to learn the real world of electronics, so you can learn how to specify parts to do the job.
  • You need to start reading specs to find the limitations like Vo range near supply rail.
  • It is assumed you know how to make a single supply work on this assignment, from what has been said or ask better question. ok?
  • Try to make one of the two suggesions work for making a 50V PS.
  • Design a high voltage Op Amp with R ratio gain of x5 is your assignment or find one. Use DigiKey since they have all the parts and a great catalog search engine.
  • Stability is an issue with uncompensated feedback amplifiers, so compensation may be needed.
  • Design a bipolar transistor design. I can suggest an inexpensive complementary pair. https://www.onsemi.com/pub_link/Collateral/UMZ1NT1-D.PDF these are a few cents, if you can find stock.
  • THere are more linear IC's than transistors in an Intel i7 and you need to start looking how to find them.
  • YOu have to search by parameters, in this case Supply voltage range
  • Here's another option ~$4 for 1
 

Thank for your time SunnySkyguy
So, by your explanation, one solution is using HV op amp such as OPA445 or OPA551.
another way is designing complementary bipolar transistor. if you can draw some simple schematic that i can figure out your mind.

Thanks again
 
Last edited:

No need for special circuits, use external NPN bipolar transistors, like this
 

Attachments

  • test OA 50V.png
    test OA 50V.png
    41.6 KB · Views: 188
  • Ctrl 1.png
    Ctrl 1.png
    23.3 KB · Views: 177
Last edited:

No need for special circuits, use external NPN bipolar transistors, like this
Basically good. I would replace R8 by a RC series circuit to turn the P voltage controller in a PI one and cancel static errors (load and temperature dependant voltage variations).
 

Thank you guys for your recommendation
I changed alittle mister_rf design and simulated it by software. it worked great. however when I implemented it in bread board, what I saw in scope was strange.. output voltage was just like a square wave signal and my design worked as a oscillator :!:
what does happened?

Power2.png
 

The error amplifier (OP) must be compensated for stable loop gain. You changed the design by removing R8, but the original design didn't work as well, because the negative OP input is driven by a voltage source and R8 doesn't provide the intended gain reduction.

P.S.: Possible compensation like below. Cascading two common emitter stages in your present circuit created a high gain and demands for a stronger compensation.

 
Last edited:

@FvM, Thanks for your suggestion
can you tell me the value of added components?
 
Last edited:

Why did you change the design? :-D
 

Attachments

  • new design.png
    new design.png
    56.7 KB · Views: 159

@mister_rf, because you feedback from output voltage to non-inverting pin of op amp. it makes design unstable. as I know, we should always feedback to inverting pin of op amp.
please follow the link below:
http://ecelab.com/circuit-regulator-opamp.htm
 

please follow the link below
There's an interesting difference between the suggested circuit and yours. The linked circuit has no external gain elements in the feedback loop, just an output stage in voltage follower configuration. So stability with an universal compensated OP can be expected, if no large output capacitors are connected.

can you tell me the value of added components
No, you can evaluate it in a simulation. The OP AC gain must be below 1, compensating for the external gain. So the resistor in the RC series circuit must be lower than the input resistor. C can be made as small as acceptable without reducing the stability. You can make it initially large and than reduce it for optimal behaviour with setpoint steps.
 

Status
Not open for further replies.

Similar threads

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Back
Top