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Design >> RF Design >> current driven devices
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Message started by Mir on Apr 17^th, 2014, 11:01am

Title: current driven devices
Post by Mir on Apr 17^th, 2014, 11:01am

current driven devices require low supply voltage .. why?

Title: Re: current driven devices
Post by aaron_do on Apr 17^th, 2014, 8:31pm

more info.

Title: Re: current driven devices
Post by Mir on Apr 18^th, 2014, 12:14am

like if i design a current driven LNA .... it will require less voltage supply as compared to that of Voltage driven LNA..
i had read it in many research papers but was unable to find the reason

Title: Re: current driven devices
Post by aaron_do on Apr 20^th, 2014, 6:01pm

When you think about current-mode or current driven, a current source has a high output impedance, and it ideally drives a circuit with a low input impedance. This will result in the maximum amount of current going from the source to the load. On the other hand, a voltage mode would be a low source impedance driving a high input impedance which results in the maximum voltage across the load.

Current-mode is therefore associated with low-impedance nodes which results in low voltages. So you need less supply headroom to maintain linear operation. But one of the fundamental rules of engineering is the no free lunch principle :P and so you have to look at what you're trading for this better linearity (usually noise performance and power consumption).

Aaron

Title: Re: current driven devices
Post by Mir on Apr 20^th, 2014, 8:42pm

thnxs... :) :)