FOD3120

onsemi

onsemi FOD3120, 1-channel optical coupling gate driver, 8-DIP (0.300", 7.62mm) through-hole package, 3 A peak output, 5000 Vrms isolation, 35 kV/µs CMTI, -40°C to 100°C operating range.

FOD3120
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[IN STOCK] In Stock: 4,601 pcs
$1.04/ pc

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Technical specifications

FOD3120 specifications
Parameter / AttributeSpecification / Value
MountingThrough Hole
Voltage - isolation5000Vrms
Voltage - output supply15V ~ 30V
Voltage - forward (Vf)1.5V
Current - peak output3A
Current - output high, low2A, 2A
Current - DC forward (If)25 mA
Operating temperature-40°C ~ 100°C
Pulse width distortion100ns
Approval agencyUL
PackageTube
TechnologyOptical Coupling
Case8-DIP (0.300\", 7.62mm)
Channels1
Rise (Fall time)60ns, 60ns
Propagation delay tpLH (tpHL)400ns, 400ns
Common mode transient immunity35kV/µs
100% Footprint Match · Solder-Ready (No PCB Redesign Needed)

Need Stock or a Drop-in Second-Source for FOD3120?

Package: DIP-8 (gate-drive optocoupler) · Pin-compatible replacements with immediate Shenzhen spot stock

Footprint Match 97%
Supply Chain & Allocation Reality:

This eight-pin row is how inverter, servo and welder drive boards cross the isolation barrier to fire their IGBTs: TLP250 from Toshiba, HCPL-3120/A3120 from the Avago lineage, FOD3120 from the Fairchild line - four houses, one socket, and a repair literature that swaps them by name. The selection axis is output current (TLP250 at a 1.5A peak against the 2.5A class of its successors) and input threshold (the 3120 triggers from a lower LED current), and the design axis is the negative gate rail that keeps Miller capacitance from re-triggering the IGBT. In repair, the row behaves; what re-fails is the rail and the bypass capacitor the procedure keeps forgetting.

Verified Pin-Compatible Replacements (3 verified alternatives)

TLP350 Toshiba DIP-8
100% Drop-in (Zero Code Change)
Availability & Target Pricing:

The Documented Upgrade in the Same Socket

Shenzhen Spot Stock (24-48h Dispatch)

Electrical & Core Specs:

The higher-output member: about +/-2.5A peak against the TLP250s +/-1.5A, aimed at 1200V IGBTs in the 20-100A class, with lower supply current - the direct upgrade path of the row.

Gate-side supply in the 10-35V class; isolation 2500V class.

Compatibility & Drop-In Notes: The substitution rule reported from inverter repair: in low-power drives the smaller part can stand in for the bigger; in mid and high-power drives the output current difference matters, although many designs carry a post-amplifier stage that softens it.
Package & Solder Footprint: Standard 8-pin gate-drive optocoupler pinout across the row.
Shenzhen Warehouse Stock & MOQ: Active Toshiba line; the forward part of the socket.
HCPL-3120 Broadcom (Avago) DIP-8
Functional Equivalent
Availability & Target Pricing:

The Other House of the Same Socket

Shenzhen Spot Stock (24-48h Dispatch)

Electrical & Core Specs:

The Avago-line drive optocoupler: about +/-2A output, direct drive of 150A/1200V IGBT modules, and a lower LED threshold (about 2.5mA) that changes the input-side resistor arithmetic.

15V to 30V gate-side supply; isolation 1414V class (the HCNW variant carries the higher figure).

Compatibility & Drop-In Notes: The input-current difference is the practical one when crossing houses: a drive resistor sized for the 250s 5mA can overdrive a 3120s LED budget - and the reverse starves. Recompute the input resistor, then treat the row as interchangeable.
Package & Solder Footprint: Same 8-pin socket; the HCNW3120 is electrically the same part in a wider isolation body.
Shenzhen Warehouse Stock & MOQ: Multi-line stock; the standard alternative of the drive-repair trade.
FOD3120 onsemi (Fairchild line) DIP-8
100% Drop-in (Zero Code Change)
Availability & Target Pricing:

The Fairchild-Line Member

Shenzhen Spot Stock (24-48h Dispatch)

Electrical & Core Specs:

The Fairchild-line drive optocoupler with the 2.5A-class output: functionally the TLP350 of the row in the onsemi lineage.

Same gate-side envelope as the row.

Compatibility & Drop-In Notes: The row rule applies: verify the input threshold figure of the exact member, recompute the LED resistor if crossing houses, and treat output current as the power-class decision.
Package & Solder Footprint: Standard 8-pin pinout.
Shenzhen Warehouse Stock & MOQ: Stocked with the row; the documented second source for A3120 designs.
Buyer & Quality Checklist for Sourcing Alternatives
  • The negative gate rail is the design, not the luxury: a VEE below emitter (the +15/-15V or +15/-8V schemes) prevents Miller-capacitance false turn-on in bridge drives. Repairs that skip the negative rail reintroduce the shoot-through the original design existed to avoid.
  • The bypass capacitor lives between pins 8 and 5 (0.1uF class) - it is in every application note and on no repair checklist; missing it turns switching transients into mysterious drive glitches.
  • Crossing houses recomputes the input resistor: Toshiba members trigger around 5mA, the 3120 family around 2.5mA - the difference is the LED and eventually the driver behind it.
  • Output current is the power-class axis: 1.5A against 2.5A peaks decides whether the part drives the IGBT gate directly or leans on a post-amplifier stage - read the schematic, not the name.
  • When a drive optocoupler fails, the IGBT usually failed first (or together): meter the gate-emitter junction and the collector path before fitting the third driver into the same board.
  • In repair inventory, the row is one drawer with one trap: isolation grade differences (HCNW and wide-body variants) mean the subs that exist on paper are not always subs on the board.
Frequently Asked Technical Questions

Q: Can TLP250 and HCPL-3120 replace each other?

A: In low-power drives yes - the reported practice is direct interchange in the 8-pin socket - with the input-resistor recomputation for the different LED thresholds (about 5mA against 2.5mA). In mid and high-power drives compare the output-current class first.

Q: What drives TLP250 output current selection?

A: The IGBT gate charge and the absence of a post-amplifier stage: 1.5A peaks suit the 50A/1200V class the TLP250 was specified for, while the 2.5A members (TLP350, FOD3120) cover 20-100A modules without help.

Q: Why do repaired inverter drives fail again at power-up?

A: Commonly the negative gate rail or the missing bypass capacitor: without VEE the Miller capacitance false-triggers the bridge, and without the 0.1uF at pins 8-5 the drive sees every switching transient. Check both before blaming the new optocoupler.

Technical details

3 A peak output for direct IGBT and MOSFET gate drive

The FOD3120 delivers a 3 A peak output current — enough to drive the gate of medium-power IGBTs and MOSFETs without an external boost stage. The 2 A source and 2 A sink capability keeps turn-on and turn-off edges symmetric, which simplifies dead-time budgeting in half-bridge and full-bridge topologies. Rise and fall times are 60 ns typical, and the maximum propagation delay is 400 ns with a pulse-width distortion ceiling of 100 ns. That timing consistency matters when paralleling multiple drivers for higher current modules — skew between channels stays inside the switching-loss budget.

5000 Vrms isolation and 35 kV/µs CMTI for industrial noise environments

With 5000 Vrms isolation and a minimum common-mode transient immunity of 35 kV/µs, this optocoupler holds its output state through the fast voltage swings on the high-side gate drive in a motor inverter or switching power supply. The UL approval covers the safety spacing for reinforced insulation in mains-connected equipment. The supply voltage range of 15 V to 30 V matches the typical gate-drive bias for IGBTs and standard MOSFET drivers. The 1.5 V typical forward voltage and 25 mA maximum forward current are compatible with logic outputs through a series resistor.

FOD3120
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