From: Winfield Hill
Subject: Re: Cheap, and badly behaved, FET op-amp needed
Date: 9 Oct 2002 14:06:43 -0700
Organization: Rowland Institute
X-Newsreader: Direct Read News 2.98
Charles DH Williams wrote...
> For years I've used LF 411 (fet input op amps) in some electronics
> practicals for students. ... Any ideas for a cheap replacement
> op-amp with similarly "educational" behaviour?
Here's my low-cost classic-style 30V JFET opamp list.
Most are dual types, which may be easier to get.
TI and Analog Devices seem good choices.
You may want to also consider CMOS-input opamps. With
these you can get even more types of bizarre behavior
These days manufacturers aren't so interested on +/-15V
supplies, or in miniDIP packages. :-( Maybe it's time
to start teaching +/-5V supplies, SMT packages and chip
Winfield Hill wrote:
> Limited choices for low-cost 36V to 42V low-offset
> voltage, fast, single JFET miniDIP opamps. :-(
> LF356A (2mV max) and LF356B (5mV) are both obsolete,
> and most competing versions as well, including LTC's
> lower-offset model.
> Motorola's MC34081BP (2mV) is "archive data" only,
> but marked "in stock" for $0.75 at Avnet Marshall,
> not a useful production part. Their MC33282, which
> was trimmed to 0.2mV, is also gone (as seems to be
> their _entire_ line of JFET amplifiers).
> AD's not too reliable a source, let's hope that LTC
> doesn't drop out...
> For miniDIPs use one of these, the LF412, LT1055 or
> AD711 types are good choices:
> max f_T qty 25
> NSC LF356N 10mV 5MHz $0.90 DigiKey
> TI TL081A 6mV 3MHz $0.80 DigiKey
> TI TL061ACP 6mV 1MHz $0.875 DigiKey
> NSC LF411CN 2mV 4MHz $1.32 DigiKey
> ON * MC34081BP 2mV 8MHz $0.75 qty 1000 *
> AD AD711JN 2mV 4MHz $1.36 qty 100
> LTC LT1055CN8 0.4mV 4.5MHz $2.25 DigiKey
> AD AD820AN 0.8mV 1.8MHz $1.91 qty 100 - in to Vee, R-R out
> NSC LF411ACN 0.5mV 4MHz $3.61 DigiKey
> AD AD711KN 0.5mV 4MHz $2.28 qty 100
> LTC LT1055ACN8 0.15mV 4.5MHz $ xx ?
> For dual miniDIPs use one of these:
> max f_T qty 25
> TI TL082CP 15mV 3MHz $0.39 DigiKey
> TI TL062CP 15mV 1MHz $0.69 DigiKey
> TI TL082ACP 6mV 3MHz $0.875 DigiKey
> TI TL062ACP 6mV 1MHz $ xxx
> TI TL082BCP 3mV 3MHz $1.32 DigiKey
> TI TL062BCP 3mV 1MHz $1.00 DigiKey
> NSC LF412CN 3mV 4MHz $1.21 DigiKey
> ON * MC34082BP 3mV 8MHz $ xx obsolete *
> AD OP282GP 3mV 4MHz miniDIP discontinued, SOIC only
> AD AD712JN 3mV 4MHz $1.84 qty 100
> AD * OP215GP 6mV 3.5MHz $ xx obsolete *
> NSC LF412ACN 1.0mV 4MHz $4.40 DigiKey
> AD AD822AN 0.8mV 1.8MHz $2.90 qty 100 - in to Vee, R-R out
> LTC LT1057CN8 0.8mV 4.5MHz $3.00 DigiKey
> LTC LT1464CN8 0.8mV 1.0MHz $2.60 DigiKey
> AD AD712KN 1.0mV 4MHz $5.43 qty 100
> LTC LT1057ACN8 0.45mV 4.5MHz $5.83 DigiKey
> AD AD822AN 0.4mV 1.8MHz $4.36 qty 100 - in to Vee, R-R out