Thin / metal film resistors
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From: Nemo on 8 Jan 2010 16:52 I notice that Susumu make really cheap metal film resistors - maybe 5 cents in one-off quantities. Do these have inferior noise performance compared to expensive metal film ones from manufacturers like Tyco? I realise they may have a worse tempco. Thank you, -- Nemo
From: John Larkin on 8 Jan 2010 19:14 On Fri, 8 Jan 2010 21:52:17 +0000, Nemo <zzz(a)nospam.nospam.nospam.nospam.co.uk> wrote: >I notice that Susumu make really cheap metal film resistors - maybe 5 >cents in one-off quantities. Do these have inferior noise performance >compared to expensive metal film ones from manufacturers like Tyco? I >realise they may have a worse tempco. > >Thank you, We use the Susumu 0.05% thinfilms that are specified for tempcos of 10 PPM. We pay about 20 cents each. Their tempcos are typically around 5 PPM. There's no reason why any thinfilm (or even thickfilm) resistor should be noisier than any other resistor. Johnson noise only depends on the resistance, and shot noise is not an issue in most cases. I wouldn't assume that the Tyco parts are better just because they're more expensive. John
From: miso on 8 Jan 2010 23:34 On Jan 8, 4:14 pm, John Larkin <jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote: > On Fri, 8 Jan 2010 21:52:17 +0000, Nemo > > <z...(a)nospam.nospam.nospam.nospam.co.uk> wrote: > >I notice that Susumu make really cheap metal film resistors - maybe 5 > >cents in one-off quantities. Do these have inferior noise performance > >compared to expensive metal film ones from manufacturers like Tyco? I > >realise they may have a worse tempco. > > >Thank you, > > We use the Susumu 0.05% thinfilms that are specified for tempcos of 10 > PPM. We pay about 20 cents each. Their tempcos are typically around 5 > PPM. > > There's no reason why any thinfilm (or even thickfilm) resistor should > be noisier than any other resistor. Johnson noise only depends on the > resistance, and shot noise is not an issue in most cases. > > I wouldn't assume that the Tyco parts are better just because they're > more expensive. > > John Isn't metal film supposed to be quieter?
From: John Larkin on 9 Jan 2010 00:27 On Fri, 8 Jan 2010 20:34:12 -0800 (PST), "miso(a)sushi.com" <miso(a)sushi.com> wrote: >On Jan 8, 4:14�pm, John Larkin ><jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote: >> On Fri, 8 Jan 2010 21:52:17 +0000, Nemo >> >> <z...(a)nospam.nospam.nospam.nospam.co.uk> wrote: >> >I notice that Susumu make really cheap metal film resistors - maybe 5 >> >cents in one-off quantities. Do these have inferior noise performance >> >compared to expensive metal film ones from manufacturers like Tyco? I >> >realise they may have a worse tempco. >> >> >Thank you, >> >> We use the Susumu 0.05% thinfilms that are specified for tempcos of 10 >> PPM. We pay about 20 cents each. Their tempcos are typically around 5 >> PPM. >> >> There's no reason why any thinfilm (or even thickfilm) resistor should >> be noisier than any other resistor. Johnson noise only depends on the >> resistance, and shot noise is not an issue in most cases. >> >> I wouldn't assume that the Tyco parts are better just because they're >> more expensive. >> >> John > >Isn't metal film supposed to be quieter? Johnson noise is Johnson noise. It only depends on the resistance and the temperature. Without voltage across a resistor, all you can have is Johnson noise. With current flowing through them, metal films definitely have well below shot noise. As far as I can tell, common thickfilm resistors don't have significant shot noise. Old carbon comps were said to have "excess noise" when they had a lot of voltage across them. I have seen datasheets that claimed that large value thickfilms, like Gohm and such, do have shot noise. I tried measuring shot+excess noise on thinfilms, thickfilms, and carbon films but couldn't resolve any. My setup should have easily resolved shot noise. John
From: John Larkin on 9 Jan 2010 01:25
On Sat, 9 Jan 2010 16:50:36 +1100, "Phil Allison" <phil_a(a)tpg.com.au> wrote: > >"John Larkin Bullshits AGAIN " >> >> >> Johnson noise is Johnson noise. It only depends on the resistance and >> the temperature. Without voltage across a resistor, all you can have >> is Johnson noise. >> >> With current flowing through them, metal films definitely have well >> below shot noise. > >** Huh ?? Makes no sense. What part of that doesn't make sense to you? John |