2SJ74-GR - P-Channel JFET Low-Noise Audio | Toshiba
Référence : 2SJ74-GR ✗ Fin de vie| Qté | Prix unitaire | Total |
|---|---|---|
| 1 | $0 | $0,00 |
| 10 | $0 | $0,00 |
| 100 | $0 | $0,00 |
| 500 | $0 | $0,00 |
| 1 000 | $0 | $0,00 |
2SJ74-GR Présentation
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-to-source voltage. Within the hierarchy of transistors, JFETs sit alongside MOSFETs as field-effect devices but offer inherently low gate leakage and low 1/f noise, which is why discrete JFETs remain favored in high-end analog front ends even in the era of integrated amplifiers. The 2SJ74 is the P-channel companion to the N-channel 2SK170, and the pair is a de-facto industry standard for discrete audio input stages.
Key characteristics of the 2SJ74-GR include its P-channel polarity, 400 mW package dissipation, and the GR Idss grading suffix, which groups devices into a defined drain current range so designers can bias input stages predictably without individual selection. The junction-type construction yields very low input bias current compared with bipolar transistors, a critical property for MM/MC phono preamplifier inputs where source impedance is high.
Architecturally, the 2SJ74 uses a silicon junction-gate structure with the gate formed as a PN junction; reverse-biasing this junction depletes the channel. Because there is no insulated gate, gate current is junction leakage only, keeping input-referred noise dominated by channel thermal noise. This is why the part excels in differential pairs, cascodes, and single-ended input stages of phono EQ and microphone preamplifiers.
Typical applications include the input differential pair of moving-coil head amplifiers, RIAA EQ preamplifier front ends, condenser microphone preamps, and discrete op-amp front-end JFET pairs in high-fidelity audio equipment.
A key design consideration is that the 2SJ74 is a discontinued/legacy Toshiba device; be sure to verify genuine-source availability and consider the Linear Systems LSJ74 as a production replacement.
This page synthesizes distributor pricing, drop-in alternatives, and practical design notes not found in the manufacturer datasheet.
Alternatives de remplacement direct pour 2SJ74-GR — même boîtier, compatible broche à broche. Les références à boîtier différent nécessitant une retouche du PCB sont exclues.
Variantes de cette série
Modèles de la même série directement compatibles avec 2SJ74-GR (même facteur de forme et même empreinte) — différant par Package, Transistor Type, Configuration, Mounting Type, Channel Type.
Outil de comparaison rapide — sélectionnez des références alternatives pour une comparaison côte à côte :
2SJ74-GR/BL
✅ Remplacement direct✓ En stock
$1.55 / unité
Voir la fiche technique →LSJ74
✅ Remplacement direct📋 Alternative de référence (hors catalogue)
2SJ74-GR Valeurs maximales et caractéristiques électriques
| Polarity | P-Channel |
| Type de transistor | JFET (Junction Field-Effect Transistor) |
| Technology | Silicon P Channel Junction Type |
| Maximum Power Dissipation (PD) | 400 mW |
| Boîtier | 2-5F1D (SC-43), 3 PIN |
| Number of Units in IC | 1 |
| Grade Suffix | GR (Idss grade classification) |
| Recommended Application | First stages of EQ amplifiers and M.C. head amplifiers |
| Type de montage | Through Hole |
| Configuration | Single FET |
Configuration des broches de 2SJ74-GR
| Broche 1 | S (Source) — Source terminal of the P-channel JFET (per Toshiba 2SJ74 datasheet pin configuration; verify lead order against the datasheet diagram before assembly) |
| Broche 2 | G (Gate) — Gate terminal; reverse-biased PN junction controls channel conduction |
| Broche 3 | D (Drain) — Drain terminal; majority of package power dissipation occurs here |
Applications typiques
2SJ74-GR convient pour 6 applications: MC Phono Head Amplifier Input Stage, RIAA EQ Amplifier First Stage, Condenser Microphone Preamplifier, Discrete Op-Amp Input Differential Pair, Active Crossover and Tone Control Front Ends, Instrumentation and Measurement Front Ends.
MC Phono Head Amplifier Input Stage
The Toshiba 2SJ74-GR is explicitly recommended by the manufacturer for the first stage of MC (moving-coil) head amplifiers. Moving-coil cartridges deliver sub-millivolt signals from very low source impedances, so the input device must contribute negligible voltage noise and essentially zero gate current noise. As a P-channel junction FET, the 2SJ74-GR provides junction-leakage-only gate current, eliminating the base-current shot noise that plagues bipolar inputs. In a typical implementation, a pair of 2SJ74-GR devices forms the input differential pair of a head amplifier with a gain of 20 to 26 dB, running at a few milliamps each well below the 400 mW dissipation limit. Matching the GR-grade Idss between the two devices preserves offset and CMRR, and the GR grade allows a predictable bias point without per-device selection. Using genuine Toshiba die or the Linear Systems LSJ74 replacement keeps the noise floor below the cartridge output.
Recommandé
RIAA EQ Amplifier First Stage
For RIAA-equalized phono preamplifiers, the first stage sets the entire signal chain's noise floor, and the Toshiba 2SJ74-GR is manufacturer-recommended for exactly this position. The RIAA feedback network places demanding load and gain requirements on the input device: it must deliver high transconductance at low drain current while contributing minimal 1/f noise in the 20 Hz to 20 kHz audio band. The junction-FET construction of the 2SJ74-GR provides low flicker noise corner and high input impedance, so the cartridge and RIAA network see a benign load. Implemented as a GR-grade differential pair with a current-mirror tail, the device operates at a few milliamps with tens of milliwatts dissipation, far within the 400 mW package rating. Because the 2SJ74 is end-of-life, designers of new EQ stages should verify stock or specify the Linear Systems LSJ74 direct replacement, which targets the same ultra-low-noise audio performance and TO-92-compatible footprint.
Recommandé
Condenser Microphone Preamplifier
Studio condenser microphones and their outboard preamps benefit from the 2SJ74-GR's combination of high input impedance and low voltage noise. The capsule presents a very high source impedance, so gate leakage must be picoamp-level to avoid charging noise and low-frequency instability - conditions a junction FET satisfies naturally since its gate current is only PN-junction leakage. A single 2SJ74-GR used as a common-source or source-follower buffer, biased in its GR-grade Idss range, drives the balanced line stage with minimal added noise and distortion. Because drain currents are typically well under 5 mA, dissipation remains far below the 400 mW rating even in the compact microphone body, keeping self-heating drift negligible. For new microphone designs, the Linear Systems LSJ74 is the recommended in-production substitute, and matched pairs are available when a differential topology is preferred for improved power-supply rejection.
Recommandé
Discrete Op-Amp Input Differential Pair
High-end discrete op-amps for audio frequently use a 2SJ74-GR P-channel JFET pair at the input to combine bipolar-like transconductance with JFET-like input impedance. Running the pair at 2 to 4 mA per device yields high open-loop gain while input bias current stays at junction-leakage levels, so feedback network values can be kept high without DC offset penalties. The GR Idss grading simplifies factory matching: selecting two devices from the same grade, or purchasing matched LSJ74 pairs, gives predictable offset and drift. With 400 mW package dissipation and typical operation at tens of milliwatts, thermal design is trivial in a TO-92 (2-5F1D / SC-43) footprint. Since Toshiba has discontinued the 2SJ74, new discrete op-amp designs should adopt the Linear Systems LSJ74, which Linear Systems specifies as a direct replacement and which is available as matched pairs for differential front ends.
Recommandé
Active Crossover and Tone Control Front Ends
In active crossovers, EQ shelving stages, and tone-control circuits that follow a phono preamp, the 2SJ74-GR can serve as a low-noise input buffer or as the input pair of a discrete gain block. Its high input impedance lets designers use large-value potentiometers and coupling capacitor networks without loading-induced frequency-response errors, while its low gate current keeps DC offsets across coupling capacitors negligible. Operating from split supplies of roughly ±15 V at a few milliamps, each device dissipates only tens of milliwatts against the 400 mW rating, so no heatsinking is needed in the 2-5F1D (SC-43) package. The GR grade's defined Idss window allows a single source-resistor value across a production run. Because the 2SJ74 is end-of-life, specify the Linear Systems LSJ74 - its officially designated direct replacement - for new board spins, keeping the same topology and bias networks intact.
Recommandé
Instrumentation and Measurement Front Ends
Beyond consumer audio, the 2SJ74-GR suits low-level measurement front ends such as hydrophone, accelerometer, and photodiode transimpedance buffers, where the source impedance is high and added noise must be minimal. The junction FET's picoamp gate leakage prevents input bias-induced errors across the source, and its low 1/f noise corner preserves signal fidelity at low frequencies important for seismic and physiological sensing. Biasing within the GR-grade Idss window with source degeneration gives stable gain over temperature, and the modest 400 mW dissipation limit is easily respected at the microamp-to-milliamp currents typical of these circuits. In the 2-5F1D (SC-43) through-hole package the part is convenient for prototyping and low-volume instruments. For designs entering production today, the Linear Systems LSJ74 provides the same role with guaranteed ongoing supply, and Linear Systems matched pairs further reduce offset trim requirements.
Recommandé
Récapitulatif des produits recommandés
Données de référence d'ingénierie pour 2SJ74-GR — comparaison, recommandations de conception et informations de conformité.
Guide de sélection
Comparaison avec les alternatives
| Paramètre | Ce produit | 2SJ74-GR/BL | LSJ74 |
|---|---|---|---|
| Package | 2-5F1D / SC-43 (TO-92 style), 3-pin | 2-5F1D / SC-43 (TO-92 style) - same | TO-92 compatible - same |
| Brand | Toshiba | Toshiba | Linear Systems |
| Polarity | P-Channel | P-Channel | P-Channel |
| Device Type | Silicon P-channel junction FET (JFET) | Silicon P-channel JFET | Ultra-low-noise P-channel JFET |
| Lifecycle Status | End-of-life (legacy stock only) | End-of-life (legacy stock only) | Active production |
| Recommended Application | EQ amplifier / MC head amplifier first stages | Same (same datasheet) | Ultra-low-noise audio/acoustic applications (direct replacement) |
Principaux différenciateurs
- Manufacturer-recommended for the most noise-critical position (vs Generic small-signal P-channel JFETs)
- Identical die with different Idss grading vs 2SJ74-GR/BL (vs 2SJ74-GR/BL)
- Production-continuity trade-off vs LSJ74 (vs LSJ74)
Notes de conception
The 2SJ74 family is end-of-life, and marketplace channels carry widespread counterfeit and unlabeled TO-92 parts sold as '2SJ74 equivalents' - the diyAudio community reports receiving unmarked devices of unknown provenance. Source only from authorized distributors or brokers with lot traceability, or migrate new designs to the Linear Systems LSJ74, which the manufacturer designates as a direct replacement. Also note the GR suffix is an Idss grade, not a variant of the die: never mix GR and BL parts in a matched pair without re-measuring or purchasing factory-matched devices.
Keep drain current and supply voltage sized so that device dissipation stays comfortably below the 400 mW package rating. Estimated: at VDS = 15 V and ID = 4 mA, dissipation is only 60 mW - about 15% of the limit - leaving ample margin for signal swing. Estimated: dissipation would approach the limit only near VDS = 50 V and ID = 8 mA, conditions far outside typical audio input-stage biasing. At audio-stage dissipation levels no heatsink is required for the 2-5F1D (SC-43) package, but avoid thermally coupling the input pair to warm regulators to prevent offset drift.
For differential input pairs in phono and head-amplifier stages, place the two JFETs physically adjacent or in thermal contact so both die track temperature, and keep gate traces short and guarded to minimize leakage and hum pickup at the picoamp gate-current level. Use 1% or better resistors in source degeneration, and design the bias network around the GR grade Idss window from the Toshiba datasheet. For layout reuse, note the Linear Systems LSJ74 shares the 3-pin TO-92-style footprint, enabling drop-in substitution on existing boards after verifying lead order.
Informations de conformité
Compliance status is not stated in the available distributor and datasheet data for this legacy Toshiba device. Legacy through-hole parts of this era may have tin-lead lead finishes; confirm with the distributor at time of RFQ.
