CA3240 Advantage over TL082?
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From: Frank-Stefan Müller on 17 Jun 2010 05:07 Hi there, a client of mine insists in using ONLY Ca3240s instead of TL082s. Anybody knows a reason exept Intersil shareholdership? Frank
From: Winfield Hill on 17 Jun 2010 06:13 Frank-Stefan_Mueller wrote... > > A client of mine insists in using ONLY Ca3240s instead of TL082s. > Anybody knows a reason except Intersil shareholdership? Most specs favor the JFET '082, but some favor the '3240. If he needs operation to the negative rail, either IN or OUT, the CA3240 gets the nod. Being a mosfet, it also has less leakage at high ambient temps. But many would consider the lack of a second source to be a strong mark against it. view in monospace font: item CA3240A TL082A input: mosfet jfet Vcm input range: to -rail: yes no to +rail: no yes output to rail? Vee: yes no Vos max: 5 6 mV Ib max: 0.64 7 nA at +70C e_n typ: 40 18 nV slew typ: 9 13 V/us f_T typ: 4.5 3 MHz Iq (both) 8.0 2.8 mA cost: $1.18 $0.43 for 100 pieces 2nd source: no yes -- Thanks, - Win
From: Frank-Stefan Müller on 17 Jun 2010 08:59 Winfield Hill schrieb: > Frank-Stefan_Mueller wrote... >> A client of mine insists in using ONLY Ca3240s instead of TL082s. >> Anybody knows a reason except Intersil shareholdership? > > Most specs favor the JFET '082, but some favor the '3240. > If he needs operation to the negative rail, either IN or > OUT, the CA3240 gets the nod. Being a mosfet, it also has > less leakage at high ambient temps. But many would consider > the lack of a second source to be a strong mark against it. > > view in monospace font: > > item CA3240A TL082A > input: mosfet jfet > > Vcm input range: > to -rail: yes no > to +rail: no yes > > output to rail? > Vee: yes no > Vos max: 5 6 mV > Ib max: 0.64 7 nA at +70C > e_n typ: 40 18 nV > slew typ: 9 13 V/us > f_T typ: 4.5 3 MHz > Iq (both) 8.0 2.8 mA > cost: $1.18 $0.43 for 100 pieces > 2nd source: no yes > > Thanks for your effort Frank-Stefan
From: Phil Allison on 18 Jun 2010 02:01 "Winfield Hill" >> A client of mine insists in using ONLY Ca3240s instead of TL082s. >> Anybody knows a reason except Intersil shareholdership? > > Most specs favor the JFET '082, but some favor the '3240. > > > item CA3240A TL082A > > e_n typ: 40 nV 18 nV ** Examination of the EIN curves for both devices shows big differences in the way noise varies with frequency. The MOSFET input device has a constantly falling curve which is quite unlike most JFET and BJT input amplifiers which have curves that remain level above a certain break frequency - usually at a few hundred Hz. See fig 18 on page 13. http://www.intersil.com/data/fn/fn1050.pdf See fig 21 on page 14. http://focus.ti.com/lit/ds/symlink/tl081a.pdf Means the MOSFET device is significantly *less* noisy above about 5 kHz than the JFET one. Could be useful to know.... ...... Phil
From: George Herold on 18 Jun 2010 12:47
On Jun 18, 2:01 am, "Phil Allison" <phi...(a)tpg.com.au> wrote: > "Winfield Hill" > > >> A client of mine insists in using ONLY Ca3240s instead of TL082s. > >> Anybody knows a reason except Intersil shareholdership? > > > Most specs favor the JFET '082, but some favor the '3240. > > > item CA3240A TL082A > > > e_n typ: 40 nV 18 nV > > ** Examination of the EIN curves for both devices shows big differences in > the way noise varies with frequency. > > The MOSFET input device has a constantly falling curve which is quite unlike > most JFET and BJT input amplifiers which have curves that remain level above > a certain break frequency - usually at a few hundred Hz. > > See fig 18 on page 13. > > http://www.intersil.com/data/fn/fn1050.pdf > > See fig 21 on page 14. > > http://focus.ti.com/lit/ds/symlink/tl081a.pdf > > Means the MOSFET device is significantly *less* noisy above about 5 kHz than > the JFET one. > > Could be useful to know.... > > ..... Phil Interesting, Thanks Phil. Say I noticed the other day that the opa134 has current noise that starts to rise dramatically with frequency above 2kHz or so. http://focus.ti.com/lit/ds/symlink/opa134.pdf See the graph at the bottom of page 4. Is this common for all jfet opamps? I've never seen other spec sheets that plot current noise vs. frequency for FET opamps. George H. |