How to simulate the noise of differential amplifier

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.ac differential amp hspice

as below is the spice sentence

X1 IN1 IN2 OUT1 OUT2 AMP1
vin1 in1 0 dc 0.75V ac=1 , 0
vin2 in2 0 dc 0.75V ac=1 , 180

.ac dec 10 1K 10g
.noise v(out1,out2) v(in1,in2) 10


but noise simulation failed, log shows
**warning**: invalid input noise source .. analysis omitted


how to simulate the noise of diff AMP. accurately
 

amplifier noise analysis testbench in spice

try this netlist, your .noise statement is wrong

X1 IN1 IN2 OUT1 OUT2 AMP1
vin in 0 dc=0 ac=1
vcom com 0 0.75
ein1 in1 com in 0 0.5
ein2 in2 com in 0 -0.5
eout out 0 out1 out2 1

.ac dec 10 1K 10g
.noise v(out) vin 10
 

simulating the noise of a differential amplifier

Thanks, flushrat

it's helpful
 

differential amplifier+netlist

i think the vin ac should be 2
if ac=1,then vdb(out1)=vdb(out2)but not the same as vdb(out)
vdb(out) maybe 3db larger then the other two
flushrat said:
try this netlist, your .noise statement is wrong

X1 IN1 IN2 OUT1 OUT2 AMP1
vin in 0 dc=0 ac=1
vcom com 0 0.75
ein1 in1 com in 0 0.5
ein2 in2 com in 0 -0.5
eout out 0 out1 out2 1

.ac dec 10 1K 10g
.noise v(out) vin 10
Click to expand...
 

differential amplifier noise analysis

vdb(out) is differential gain, whereas vdb(out1) is single-end gain
so vdb(out) must be 3dB larger than vdb(out1)

 

what is the ein ?

why did you add it, is it neccessary for the noise analysis?????
 

flushrat said:
try this netlist, your .noise statement is wrong

X1 IN1 IN2 OUT1 OUT2 AMP1
vin in 0 dc=0 ac=1
vcom com 0 0.75
ein1 in1 com in 0 0.5
ein2 in2 com in 0 -0.5
eout out 0 out1 out2 1

.ac dec 10 1K 10g
.noise v(out) vin 10
Click to expand...


dear flushrat,

i'm new in analog ic design. can u tell me are there books or manuals that tell what is ein, in1, com etc. when and where to write them in ur netlist. i tried to find books about ic design but only found few books with few examples on how to write netlist in hspice. if u do have a soft copy about that book or manual can u pls upload it here.

regards
 

ein is the differential input . Using e elements is better than using two vsources in simulation (refer to "A test bench for differential circuits" on www.designers-guide.com )

It is not necessary for noise analysis.

Ashtaroth said:
what is the ein ?

why did you add it, is it neccessary for the noise analysis?????
Click to expand...

Added after 2 minutes:

refer to hspice manual

 

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