Product Overview
Motorola MPF3821 - N-Channel Silicon JFET, 50V, TO-92
Condition
New. The photo shows a representative unit from our stock.
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Product Overview
The MPF3821 is an N-channel silicon junction FET in a TO-92 plastic case (Motorola Case 29), published as the plastic-package equivalent of the 2N3821 low-leakage JFET on the MPF3821/MPF3822 small-signal FET data.
100 are on the shelf, sold each. The representative unit photographed is a black TO-92 lettered MPF on the top line, 3821 on the second and the Motorola batwing followed by 312 on the third; turn it over and the rounded rear face carries a single small circular mould mark with a cross through it and nothing else. 312 is a marking string on this page and will stay one - the published data behind this listing decodes nothing about Motorola-era stamped codes, so reading a date into those three digits is something we leave to other sellers. The three leads leave the body straight and parallel at full length, untrimmed, and photograph bright silver in hand and darker grey against the clear crinkled wrap.
Key Features
- Type: N-channel silicon junction field-effect transistor
- V(BR)GSS: 50 V (per the published Motorola MPF3821/MPF3822 small-signal FET data)
- IDSS: 0.5 to 2.5 mA (per the same published data)
- VGS(off): -4.0 V maximum (per the same published data)
- IGSS: -0.1 nA at VGS = -30 V, 25 degC (per the same published data)
- ID: 10 mA class part (per the same published data)
- Package: TO-92 plastic, Motorola Case 29, three through-hole leads
- Published as the plastic-package equivalent of the 2N3821 low-leakage JFET
- Body marking on the unit photographed: MPF, 3821, Motorola batwing, 312, with a small crossed circular mould mark on the rounded rear face
- No lead assignment is quoted here; the data we work from does not publish one, so confirm gate, source and drain against the published MPF3821/MPF3822 data before you solder
- Verify against Motorola's published MPF3821/MPF3822 small-signal FET data before designing in.
Applications
- High input impedance buffers and source followers
- Electrometer and low leakage front ends
- Sample and hold and analog gate service
- Repair or rebuild of instrument input stages specified around a 2N3821
Frequently Asked Questions
How many should I order?
Order the count the build needs. 100 are here, sold one at a time, which is enough that matching a handful for IDSS on a meter and keeping the rest as spares is a reasonable thing to do on one order rather than two. Shipping is $8 flat rate and free on orders over $28, so small parts like this ship smartest as part of a larger order.
Can I drop this in where a 2N3821 was?
Electrically the sheet points that way, mechanically you have to look. The published MPF3821/MPF3822 data presents this part as the plastic-package equivalent of the 2N3821 low-leakage JFET, which is what the MPF prefix and Motorola Case 29 designate - a TO-92 plastic body, not a metal can, so the footprint, the lead circle and any grounding you were getting from a can are not carried over. Two numbers to hold against your circuit before you commit: IDSS runs 0.5 to 2.5 mA and VGS(off) is -4.0 V maximum on the published data, so a bias network trimmed for a different IDSS group will want revisiting. We quote no gate, source and drain order here because the data we work from does not publish one for this package; check it before you solder. What ships is the JFET alone, in ones.
A hundred plastic JFETs whose whole job is to leak a tenth of a nanoamp and otherwise stay out of the way.
