From: Robert Strand
Subject: Re: Confused in Massachussets, 2n7000 data sheet
Date: Tue, 07 Jan 2003 16:40:40 +1100
Organization: ihug ( New Zealand )
NNTP-Posting-Date: Tue, 7 Jan 2003 05:43:16 +0000 (UTC)
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> 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
Agreed on those points as well.