Stiff voltage source

[khatus]

Here, What is meant by a stiff voltage source?

 

[KlausST]

Hi,

I translate it as "low impedance". It means "low voltage drift" when current is drawn.
In other words: Constant voltage, stable voltage.

Klaus

 

[D.A.(Tony)Stewart]

"Stiff"= resists change from influence
Lower impedance relative to the load.

For PSU's and V regulators or bias V source and audio power amplifers"
% Load regulation error = RS(source) / RL (load) * 100% = 1/ damping factor for amp/speaker

If a Si diode's incremental resistance is in the bulk region >> 0.6V or >> 1mA then the low bulk resistance begins to dominate Vf, which depends on size or power rating of diode

"Stewart's Theorem"
Rs ~ 0.5 / P max (rating) +/-50% covers most forward diodes for Si, LEDs and Vce(sat) from ESD tiny diodes to Hockey puck diodes. (Zeners and TVS have an V offset but have a bigger voltage knee factor that varies this rule of thumb.

Interactive Simulation http://tinyurl.com/yqx74wqz

e.g. for sub-Woofers you need high damping factor 200~1000
which means the cone EMF won't affect the voltage applied by this ratio within the amplifier's bandwidth. So the cone is stiff due to the low impedance of the power amp ratio to speaker impedance.

Likewise for transistor bias where 0.1% to 10% may be adequate depending on Specs. for source variation to desired response. (and all tolerances involved).

 

[barry]

"Stiff"= resists change from influence
Lower impedance relative to the load.

For PSU's and V regulators or bias V source and audio power amplifers"
% Load regulation error = RS(source) / RL (load) * 100% = 1/ damping factor for amp/speaker

If a Si diode's incremental resistance is in the bulk region >> 0.6V or >> 1mA then the low bulk resistance begins to dominate Vf, which depends on size or power rating of diode

"Stewart's Theorem"
Rs ~ 0.5 / P max (rating) +/-50% covers most forward diodes for Si, LEDs and Vce(sat) from ESD tiny diodes to Hockey puck diodes. (Zeners and TVS have an V offset but have a bigger voltage knee factor that varies this rule of thumb.


View attachment 187409

Interactive Simulation http://tinyurl.com/yqx74wqz

e.g. for sub-Woofers you need high damping factor 200~1000
which means the cone EMF won't affect the voltage applied by this ratio within the amplifier's bandwidth. So the cone is stiff due to the low impedance of the power amp ratio to speaker impedance.

Likewise for transistor bias where 0.1% to 10% may be adequate depending on Specs. for source variation to desired response. (and all tolerances involved).

Are you interviewing for a job? ‘Diode incremental resistance’? ‘sub-woofer damping factor’? ‘amplifier bandwidth’? None of this has anything to do with the OP’s question “what is meant by a stiff voltage source”.

 

[Easy peasy]

@ Barry, he did answer the question in the 1st paragraph, your text is not helpful in any way.

 

[D.A.(Tony)Stewart]

Are you interviewing for a job? ‘Diode incremental resistance’? ‘sub-woofer damping factor’? ‘amplifier bandwidth’? None of this has anything to do with the OP’s question “what is meant by a stiff voltage source”.

I guess you were not expecting a relevant detailed explanation with related usage.
Bias has everything to do with load regulation. I could have expanded on how hFE Re loads the base bias, but I'm sure his text covers that. I only wrote what some others may appreciate.

I'll try to be as short as the question next time. maybe

 

[crutschow]

What is meant by a stiff voltage source?

Small change in voltage (well within the tolerance of the system requirements) with a change in load current.

 

[danadakk]

V source with a Rsource resistance. If Rsource = .1 ohms then .... red line of voltage out.

Solid line if Rsource 1 ohm, not as "stiff", eg V load drops/changes more with load changes.

Regards, Dana.

 

[D.A.(Tony)Stewart]

Ideal Voltage sources are 0 Ohms, infinite current.

Therefore the metric for stiffness is Rs , series resistance, including all batteries, voltage regulators and Thevenin equivalent resistance in voltage dividers.


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