2SJ74-GR P-Channel JFET Low Noise Audio | Toshiba
MPN: 2SJ74-GR/K170-GR ✗ End of Life| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $5.88 | $5.88 |
| 10 | $5.29 | $52.90 |
| 100 | $4.7 | $470.00 |
| 500 | $4.12 | $2,060.00 |
| 1,000 | $3.53 | $3,530.00 |
2SJ74-GR/K170-GR Overview
A JFET (junction field-effect transistor) is a voltage-controlled semiconductor device in which current flows through a channel whose conductivity is modulated by the gate-source voltage. Within the amplifier signal-chain hierarchy, the 2SJ74-GR belongs to the small-signal JFET family, sitting above discrete resistors and below full integrated amplifier ICs in power management of analog front ends. JFETs are prized in audio design for their extremely low input bias current, high input impedance, and naturally smooth transfer characteristics.
The defining feature of the 2SJ74-GR is its ultra-low noise figure, which made it the industry reference for phono preamplifier input stages, moving-coil head amplifiers, and differential input pairs in high-end power amplifiers. The GR grade suffix denotes a medium IDSS bin (4 mA to 8 mA), while the BL grade offers higher current (6 mA to 12 mA) for stages needing greater transconductance. Its complementary N-channel partner is the 2SK170, and the pair 2SK170/2SJ74 is the classic Toshiba complementary audio JFET set.
Architecturally, the device is a diffusion-type silicon P-channel junction FET optimized for small-signal linearity rather than switching speed. The tight IDSS binning supports matched-pair selection, which is critical in differential and cascode topologies where offset and second-harmonic cancellation depend on device matching.
Typical applications include phono cartridge preamplifiers, microphone preamps, active crossover input buffers, and discrete op-amp input stages in audiophile equipment. Designers commonly used the 2SK170-GR N-channel counterpart alongside it for complementary push-pull stages.
A key design consideration: Toshiba has discontinued the 2SJ74 family, so new designs should verify stock and consider the Linear Systems LSJ74 drop-in replacement, which is pin-compatible in TO-92.
This page synthesizes distributor pricing, drop-in alternatives, and practical design notes not found in the manufacturer datasheet.
Drop-in alternatives for 2SJ74-GR/K170-GR — same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
Variants in this series
Same-series models that are drop-in compatible with 2SJ74-GR/K170-GR (same form factor and footprint) — differing in Package, Configuration, Transistor Type, Mounting Type, Grade Suffix.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
2SJ74-GR/BL
✅ Drop-In✓ In Stock
$1.55 / Unit
View Datasheet →2SJ74-GR
✅ Drop-In✓ In Stock
Contact for price
View Datasheet →LSJ74
✅ Drop-In📋 Reference alternative (not in catalog)
LSK170A
✅ Drop-In✓ In Stock
$0.94 / Unit
View Datasheet →2SJ74-GR/K170-GR Maximum Ratings & Electrical Characteristics
| Transistor Type | P-Channel JFET (Junction FET) |
| Polarity | P-Channel |
| Drain-Source Voltage (VGDS) | -50 V |
| Drain Current IDSS (GR grade) | 4 mA to 8 mA |
| Power Dissipation (PD) | 400 mW |
| Package | TO-92 (2-5F1D / SC-43, 3-pin) |
| Number of Units | 1 |
| Primary Application | Low noise audio amplifier |
| Mounting Type | Through Hole |
| Configuration | Single |
| Grade Suffix | GR (IDSS 4-8 mA bin) |
| Complementary N-Channel Part | 2SK170-GR |
2SJ74-GR/K170-GR Pin Configuration
| Pin 1 | S — Source terminal of the P-channel JFET |
| Pin 2 | G — Gate terminal (junction control electrode) |
| Pin 3 | D — Drain terminal of the P-channel JFET |
Typical Applications
2SJ74-GR/K170-GR is suitable for 6 applications: Phono Preamplifier Input Stage, Differential Input Pairs in Power Amplifiers, Cascode and Current-Mirror Circuits, Microphone Preamplifier Front Ends, Active Crossover and Line-Level Buffers, Discrete Op-Amp and Instrumentation Front Ends.
Phono Preamplifier Input Stage
The 2SJ74-GR was the canonical input device for moving-magnet and moving-coil phono preamplifiers, where cartridge source impedances of a few hundred ohms to 47 kOhm demand ultra-low input-referred voltage noise. Its GR-grade IDSS of 4-8 mA provides high transconductance at low drain voltage, and the JFET gate draws virtually zero bias current, so no DC flows through the cartridge coil to cause distortion. Operated at IDSS with 10-15 V drain voltage, the device achieves its minimum noise figure. For moving-coil duty, the higher-IDSS BL grade reduces voltage noise further. With Toshiba production ended, the Linear Systems LSJ74 is the drop-in substitute; use factory-matched pairs to keep differential offset below a few millivolts across gain stages.
Recommended
Differential Input Pairs in Power Amplifiers
High-end power amplifier front ends, including Nelson Pass designs widely discussed on diyAudio, use 2SK170/2SJ74 pairs as differential input transistors. The 2SJ74-GR's low noise and tight IDSS grading allow matched pairs that cancel second-harmonic distortion and minimize input offset, which directly reduces DC offset at the speaker output. Its -50 V rating supports front-end rails of approximately ±30 V with headroom for startup transients. The JFET's square-law transfer characteristic yields benign, low-order harmonic behavior preferred in audiophile designs. When populating new boards, pair the 2SJ74-GR with its 2SK170 counterpart, matching IDSS within 0.5 mA per leg; the LSJ74 remains available for production continuity.
Recommended
Cascode and Current-Mirror Circuits
In two-stage cascodes, the 2SJ74-GR commonly serves as the upper cascode device, shielding the lower gain JFET from drain-voltage modulation and Miller capacitance, which raises bandwidth and linearity. Its low gate leakage (picoamperes typical for junction FETs) preserves the low-noise benefit of the cascoded stage. In current mirrors and cascode current sources, the GR grade's predictable 4-8 mA IDSS supports simple IDSS-referenced biasing without precision resistors. Designers should keep the cascode device's VDS well below the -50 V maximum and observe the 400 mW package dissipation limit, which at typical audio front-end currents is not restrictive. The TO-92 through-hole package also simplifies hand-matching before installation.
Recommended
Microphone Preamplifier Front Ends
Condenser and dynamic microphone preamplifier inputs benefit from the 2SJ74-GR's combination of near-zero gate current and low voltage noise, preserving signal-to-noise ratio for low-output microphones. In discrete FET-input preamp front ends, the device is configured as a common-source or differential amplifier followed by bipolar or operational gain stages. Its high input impedance (gigaohm-range gate bias resistance) permits direct coupling to FET-capsule condenser microphones without loading the capsule. The GR grade suits standard 200-ohm balanced microphone sources; for extremely low-impedance ribbon microphones, the BL grade's higher IDSS improves noise performance. Verify bias points with measured device IDSS, since grading spread within the bin materially shifts the operating point.
Recommended
Active Crossover and Line-Level Buffers
Line-level active crossovers and output buffers in audiophile systems employ 2SJ74-GR source followers or JFET-input stages for their soft clipping characteristic and absence of crossover distortion artifacts. Running the device as a source follower at several milliamps of standing current yields low output impedance with excellent linearity into typical 10-50 kOhm load impedances. The 4-8 mA GR-grade IDSS provides sufficient bias headroom without excessive dissipation in the 400 mW TO-92 package. Because JFET VGS(off) varies between units, designers should include source degeneration or servo trim for DC offset control. Replacement stock for service work is best satisfied with Linear Systems LSJ74 parts, which preserve both pinout and audio character.
Recommended
Discrete Op-Amp and Instrumentation Front Ends
Discrete op-amp modules and instrumentation amplifier front ends historically used 2SK170/2SJ74 complementary pairs as the input differential stage, combining JFET input impedance with bipolar second-stage gain. The 2SJ74-GR contributes the P-channel half, enabling input common-mode ranges approaching the negative rail and picoampere input bias currents essential for high-impedance sensors and photodiode transimpedance applications. Its GR grade IDSS of 4-8 mA balances transconductance against standing power in compact modules. For precision designs, select and match devices by measured IDSS and transconductance rather than relying on grade bins alone. New builds should standardize on LSJ74 to secure long-term supply, reserving remaining genuine 2SJ74-GR inventory for legacy repair work.
Recommended
Recommended Products Summary
Engineering reference data for 2SJ74-GR/K170-GR — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | 2SJ74-GR | 2SJ74-GR/BL | LSJ74 | LSK170A |
|---|---|---|---|---|---|
| Package | TO-92 (2-5F1D/SC-43) | TO-92 - same | TO-92 - same | TO-92 - same | TO-92 - same |
| Brand | Toshiba | Toshiba | Toshiba | Linear Systems | Linear Systems |
| Channel Polarity | P-Channel | P-Channel | P-Channel | P-Channel | N-Channel (complement) |
| Lifecycle Status | EOL (discontinued) | EOL | EOL | Active production | Active production |
Key Differentiators
- Genuine Toshiba original audio JFET (vs LSJ74)
- Tight GR IDSS grading of 4-8 mA (vs 2SJ74-GR/BL)
- P-channel polarity for complementary pairs (vs LSK170A)
Design Notes
The 2SJ74-GR is discontinued and the aftermarket contains many counterfeit or re-marked parts, which typically show IDSS far outside the 4-8 mA GR bin and elevated noise. Always measure IDSS at VDS = -10 V with the gate shorted to source before committing devices to a matched input stage, and reject parts deviating more than 1 mA from their bin. For matched pairs, select within 0.5 mA IDSS to keep differential-pair offset manageable. If authenticity cannot be verified, specify the Linear Systems LSJ74 instead.
Estimated: the 400 mW TO-92 dissipation limit allows, for example, 6 mA of drain current at up to roughly 60 V of VDS in theory, but practical audio designs keep VDS at 10-20 V and IDSS-level current, yielding 60-120 mW of dissipation and negligible junction heating. The real design constraint is not power but the -50 V drain-gate maximum: in power-amp front ends with ±30 V rails, verify that startup transients and input-signal swings cannot drive the drain-gate junction beyond rating, since gate avalanche permanently degrades the low-noise characteristic.
In phono and microphone input applications, keep the gate lead connection as short as possible and guard the gate node with a grounded shield trace to control hum and leakage. Because JFET gate leakage rises sharply with temperature, route the 2SJ74 away from hot components such as regulators and power resistors; cooler operation preserves the picoampere-level input bias that the design depends on. For through-hole TO-92 layouts, allow lead spacing per the 2-5F1D/SC-43 package drawing in the Toshiba datasheet and avoid mechanical stress on the gate lead during forming.
Compliance Information
Part is discontinued (EOL); no current environmental compliance declarations are published in the available verified data. Original-era through-hole production predates universal RoHS documentation. For RoHS-certified equivalents, use Linear Systems LSJ74 with current compliance declarations.
