how to calculate power in circuit

aryna

Joined Dec 10, 2020
19
hi everyone , im very confuse with this circuit, i need to calculate P=IV, in this circuit it shows many current and, is it correct if i took current from VDD
i understand that for using P=IV, the voltage from power supply is V=8V, and my question is it correct if i took current from VDD, or i need to add all the current from all component?

Attachments

• 122.3 KB Views: 5

ericgibbs

Joined Jan 29, 2010
11,628
hi aryna,
Welcome to AAC
Please post your LTS asc file and we can run the simulation and suggest a method.
E

aryna

Joined Dec 10, 2020
19
this is the design , and also i attach the opa227 library, pls help me everyoneeee

Attachments

• 2.4 KB Views: 2
• 14.3 KB Views: 2

ericgibbs

Joined Jan 29, 2010
11,628
hi a,
The power supply connections don't make any sense.?
Why have you used two labels for each supply.?

I will edit and run and post back.
E

ericgibbs

Joined Jan 29, 2010
11,628
hi aryna,
Before I post a solution, can you confirm this is a Homework assignment.?

E

aryna

Joined Dec 10, 2020
19
yes it is homework

aryna

Joined Dec 10, 2020
19
because i just trying to made me more understand
VCC=VDD
VEE=VSS
because opa227 in VCC and VEE

ericgibbs

Joined Jan 29, 2010
11,628
hi aryna,
As this is Homework I can only guide you thru the problem, not give you the final answer, OK.
So could you first redraw your circuit like this image, then we can do the next step.
E

Attachments

• 15.1 KB Views: 7

aryna

Joined Dec 10, 2020
19
okay , i already redraw it, then what should i do?

ericgibbs

Joined Jan 29, 2010
11,628
hi,
Add these two lines, run the sim,check the error log.
E

aryna

Joined Dec 10, 2020
19
may i ask why the voltage supply draw like that?

ericgibbs

Joined Jan 29, 2010
11,628
may i ask why the voltage supply draw like that?
Hi,
Just my preferred way.
E

aryna

Joined Dec 10, 2020
19
i dont know why become like this

ericgibbs

Joined Jan 29, 2010
11,628
hi,
I did say copy my drawing, you missed out this.
E

aryna

Joined Dec 10, 2020
19
oh sorry i missed out, and i already run it, how to check the error log.

ericgibbs

Joined Jan 29, 2010
11,628
hi,
Look at thsi image.
To see the Power plot.
Run the sim.
Place your cursor on the V3 symbol, press the ALT and left mouse click.
OK.?
E

Attachments

• 97.1 KB Views: 4
• 19.6 KB Views: 3

aryna

Joined Dec 10, 2020
19
okay i get it, but why the value of power become negative for V3= -0.0540892, and may i ask a little bit explanation of this
.meas TRAN arg1 AVG (I(V3)*V(pv))
And why mine like this

aryna

Joined Dec 10, 2020
19
so basically the power is negative because the current negative? can you explain to me why? is it correct to measure power consumption in is P = I(Vdd)*V(vdd)

ericgibbs

Joined Jan 29, 2010
11,628
hi,
.meas TRAN arg1 AVG (I(V3)*V(pv))

This is explained in the Help files. measure,
TRAN for analysis method
arg1 is a name for a Variable
AVG is the Average value
of I(V3) * V(pv)

How do you get a run time of 5.4 seconds .???

it should be

Your power values are much to high,,, ~ 7 Watts is wrong,

LTSpice chooses the direction of the current so it may sometimes give a negative value, for power it must be positive.

Look at this and double check.

Attachments

• 198.8 KB Views: 1