From: Winfield Hill
Subject: Re: Confused in Massachussets, 2n7000 data sheet
Date: 7 Jan 2003 07:40:47 -0800
Organization: Rowland Institute
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Robert Strand wrote...
> Hi Win,
>> Page 4 has a graph, Normalized Drain Source Resistance vs Temperature.
>> The x-axis is temperature and y-axis shows r_DSn = r_DS(Ta)/r_DS(25C),
>> the ratio of Rds(T) to Rds at 25C, which is fine. We see four plots,
>> labeled delta-V 0.5V, 1V, 2V and 3V, where delta-V = V_GS - V_GS(To),
>> and also V_GS(To) at I_D = 1mA. Whew, what's that about? Are they
>> showing the variation of R_ds(on) with temperature for four different
>> gate voltages, above some (linear operation) gate-voltage threshold?
>> I.e., if it takes Vgs = 2.0V to get 1mA linear conduction, then are
>> these Rds(on) plots for Vgs = 2.5, 3.0, 4.0 and 5.0 volts?
> Win, your interpretation is correct. The both Vgs and R_ds(on) are
> normalized. V_GS(To) is the voltage when Id=1mA, what is unclear is
> whether this is at TA or 25C. I have a feeling it's a 25C and this
> might explain the negative R_ds(on) TC for low deltaV, since V_GS(To)
> has a negative tempco, and also the linearization of R_ds(on) with T
> at higher deltaV. R_ds(on)(25C) is the resistance at 25C and
> Vgs = deltaV + V_GS(To), R_ds(on)(TA) is the resistance at TA and
> delta Vgs = deltaV + V_GS(To).
>> Page 5 has an Rds(on) vs. Vgs plot; here Rds plots to about
>> 13, 8.5, 6 and 5 ohms respectively. The page 4 plot shows a strong
>> negative Rds tempco for ...etc.
> Agreed on those points as well.