OP-AMP questions about loading capacitor and resistor

[mediatek]

OP-AMP question ?

Sorry for ask two stupid question :
If loading is capacitor , what kind of op-amp architecture I need for this loading?
If loading is resistor , what kind of op-amp architecture I need for this loading?

 

[eternal_nan]

OP-AMP question ?

As far as I know, the only difference in approach is that you don't need a low-impedance output stage (like emitter follower or class b/ab amplifyer) for the first case but you do for the second.

 

[avinash]

Re: OP-AMP question ?

if your resistive load is quite high,you can use high o/.p impedance opamp i.e a transconductance.if your ressistive load is low tou have to use low o/p impedance opamp.

 

[tia_design]

Re: OP-AMP question ?

Can Class AB is ok for both high Capacitive load and low resistive load?

 

[viswa]

Re: OP-AMP question ?

for resistive loading,even if loading is high because of low o/p impedance of opamp,there is mismatch.so ,to avoid this safely use an buffer amplifier to separate load from opamp in both cases to avoid problems.

 

[yeechyan]

OP-AMP question ?

Try OTA for capacitive load.

 

[lakeoffire]

OP-AMP question ?

For op-ams, we generally care about voltage gain. So whether you need an op-am with high or low output impedance depends on the loading impedance compared to the op-am's output impedance. When loading impedance is low, a buffer will be required to transfer high op-am output impedance to low.

 

[jiangwp]

Re: OP-AMP question ?

Maybe , only base on the loading , the answer is not right.

For a unity gain OP(with the feedbak of OP) , its output is decreseing very low if the close loop gain is large. Then the output impedence of op(open loop) may be very large.

So selection for a structure of OP is not fit only based on the loading.

The feedbak type and colse loop (loop gain) also is a very important factor.

 

[srivatsan]

Re: OP-AMP question ?

From my experience:
For Capacitive: OTA
For REsistor: OTA with CLass AB.

srivats

 

[cliffj]

Re: OP-AMP question ?

For a heavy resistor load, a buffered amp is needed. Try class AB for better driving efficiency. Common source N&P output pair. You can also simpliy try with a common drain output stage at the expense of output swing. For a heavy cap load, I think better you should learn more techniques in compensating since it always affect your bandwidth & stability.

 

[Ravi Karadi]

Re: OP-AMP question ?

i think transconductance op amp is good