What is the meaning of the term "ground current"

[iVenky]

I was reading about a circuit and it says the circuit ground current is only 30 mA. What does this mean?

Thanks in advance.

 

[hshah8970]

Ground current is any unwanted current in the ground line. Could be a cause of ground loops, noise, leakage, or any imperfection with the circuit.

 

[erikl]

Ground current is any unwanted current in the ground line.

Also, the total current consumption of the circuit could be meant (total current from power supply through the circuit to GND).

 

[dick_freebird]

Particularly in positive voltage regulators, the supply current
is very load dependent while the ground (negative supply)
is a roughly fixed overhead, and the more useful spec for
internal power consumption at no-load.

 

[iVenky]

I have got an another doubt- I read in one of the papers that the pass transistor that we use in LDO reduces power consumption due to quiescent current. How is that so?

Thanks in advance.

 

[erikl]

Re: LDO reduces power consumption due to quiescent current

I think this is a rather unlucky - or incompletely rendered? - phrasing.

One could perhaps say that (the pass transistor of) an LDO - being a series regulator - allows for reduced power consumption due to low quiescent current in a no or low load situation, in comparison to a parallel regulator.

 

[iVenky]

I can't understand how pass transistor contributes to reduction in quiescent current. I think it those feedback resistors R1 and R2 that is connected parallel to load is responsible for the current flowing through the pass transistors. So I mean if R1 and R2 are large then quiescent current should be low right?

Thanks a lot.

 

[erikl]

Re: ... how pass transistor contributes to reduction in quiescent current

I can't understand how pass transistor contributes to reduction in quiescent current.

Same for me.

I think it those feedback resistors R1 and R2 that is connected parallel to load is responsible for the current flowing through the pass transistors. So I mean if R1 and R2 are large then quiescent current should be low right?

Right. An LDO consists of 3 essential parts: 1. the voltage divider (R1 and R2), 2. the error amplifier (EA), and 3. the control element (the pass transistor). The quiescent current only depends on 1. & 2. No.3 -- the pass transistor -- actually provides the current through R1 & R2, but doesn't really contribute to the quiescent current (at least if it's a FET, not a BJT) -- it just provides the additional load current.

 

[dick_freebird]

A PNP LDO requires bias current that's determined by worst
case hFE (in or near sat) and can be large. A PMOS LDO only
needs enough current to keep the reference and error amp
lit up, plus dynamic (gate slew, load-step) margin.

So choice of pass transistor technology (high-beta PNP,
MOS, ???) does affect ground current in the end.

 

[glenjoy]

A ground current is an unwanted current.