s******e
发帖数: 2181 | 1 需要设计一个由弱电压来控制强输出电流的电路
输入电压大概模5v，低频；输出电流要求最高能达到500mA
我找了场效应管，因为它是电压控制电流型，可是场效应管的增益太低了，我找到输出
最大振幅的只有100mA的管子。
想问问大家还有什么建议，是不是简单的一级放大电路没法实现呢？ |
a*****s
发帖数: 6260 | 2 一级怕是不顶. 怎么也要个运放+反馈电路吧
【在 s******e 的大作中提到】
: 需要设计一个由弱电压来控制强输出电流的电路
: 输入电压大概模5v，低频；输出电流要求最高能达到500mA
: 我找了场效应管，因为它是电压控制电流型，可是场效应管的增益太低了，我找到输出
: 最大振幅的只有100mA的管子。
: 想问问大家还有什么建议，是不是简单的一级放大电路没法实现呢？
|
f*****0
发帖数: 489 | 3 you have two issues to solve, both are very easy.
a) use an opamp where you pick up the feedback via a current sampling
resistor in the same loop with the load. vs. the traditional topology, you
need just one more resistor.
b) find a high current output opamp. I would look into high speed dsl
drivers. ad815 (preferred in a sip package, not soic), tpa6120/ths6012, etc.
most of those adsl drivers are duo opamps with high slew rates and high
current capabilities.
now, if that's difficult for you (t |
f*****0
发帖数: 489 | 4 "是不是简单的一级放大电路没法实现呢？"
sure. just put a bjt in front of it and you can easily control the gain. |
s******e
发帖数: 2181 | 5 that's good. thank you so much!
you can send the schematics to my mail box: w******[email protected] |
s******e
发帖数: 2181 | 6 that's good. thank you so much!
you can send the schematics to my mail box: w******[email protected] |
f*****0
发帖数: 489 | 7 on further reflection, I think it is much easier for you to use one of those
audio power IC (tda2030, tda2003, lm1875, etc.). they are usually in a
to220-5 package, and you need a few resistors to get it to work. they are
10w power amps into 8ohm so it shouldn't be difficult to drive 500ma (unless
your load is super tough). |
f*****0
发帖数: 489 | 8 here is how "current feedback" works.
R1 is your load, R2 is the sampling resistor that converts the current going
through R1, I1, into a voltage signal to be fed back the inverting end of
the opamp through R6/R3.
so it follows that
I1*R2*R6/(R6+R3)=Vin.
or I1=(1+R3/R6)*Vin/R2.
I typically choose R2 to be < 1/10 of R1, and R3/R6 will depend on what
opamps you use and what input impedance you need.
if you use a regular voltage feedback opamp, I would chose R3=10k.
if no DC blocking capacitor is u |
s******e
发帖数: 2181 | 9 that's good. thank you so much!
you can send the schematics to my mail box: w******[email protected] |
