2SJ74 - P-Channel Low-Noise Audio JFET | Toshiba
Артикул: 2SJ74 ✗ Снят с производства| Кол-во | Цена за ед. | Итого |
|---|---|---|
| 1 | $2.1 | $2,10 |
| 10 | $1.89 | $18,90 |
| 100 | $1.68 | $168,00 |
| 500 | $1.45 | $725,00 |
| 1.000 | $1.25 | $1.250,00 |
2SJ74 Обзор
A JFET (junction field-effect transistor) is a voltage-controlled semiconductor device that regulates current flow through a channel using an electric field at the gate junction. Within the power-management and signal-chain hierarchy, small-signal JFETs such as the 2SJ74 sit in the discrete semiconductor family, positioned as input devices ahead of operational amplifiers and gain stages. Their defining trait is an extremely low input noise density and high input impedance, which bipolar transistors cannot match at the input of a high-gain audio stage.
The key feature set of the 2SJ74 centers on its low-noise performance: Toshiba's datasheet explicitly targets low-noise audio amplifier applications, and the part is recommended for the first stages of EQ amplifiers and MC (moving-coil) head amplifiers, where the input device's noise floor directly sets overall system signal-to-noise ratio. The 25 V rating covers typical phono-stage and preamplifier supply rails, while the 20 mA current rating supports Class-A operation of the input stage for linearity.
Technically, the 2SJ74 is a silicon P-channel junction-type device, and its large transconductance at low drain current is what delivers the ultra-low equivalent input noise voltage prized in vinyl-era and modern high-end audio designs. Toshiba grades the device into ranks (such as BL and GR) by IDSS range, allowing designers to build matched or complementary pairs.
Typical applications include first-stage EQ amplifier inputs, moving-coil and moving-magnet phono head amplifiers, microphone preamplifier input buffers, and symmetric low-noise amplifier front ends. Complementary use with the N-channel 2SK170 is the classic pairing in audio engineering.
Design consideration: because JFET IDSS varies significantly between units, always verify the IDSS rank marking and, for differential stages, select matched pairs to minimize DC offset and drift.
This page synthesizes verified distributor data, drop-in alternatives, and practical design notes not found in the manufacturer datasheet.
Аналоги без доработки для 2SJ74 — тот же корпус, pin-to-pin совместимость. Компоненты в других корпусах, требующие переработки PCB, исключены.
Варианты в этой серии
Модели той же серии, совместимые без доработки с 2SJ74 (тот же форм-фактор и посадочное место) — отличается по Package, Mounting Type, Channel Type, Configuration, Technology.
Инструмент быстрого сравнения — выберите альтернативные компоненты для сравнения бок о бок:
2SJ74-BL
✅ Прямая замена✓ В наличии
$2.94 / шт.
Открыть даташит →2SJ74-GR
✅ Прямая замена ⚠️ Характеристики не проверены✓ В наличии
Уточнить цену
Открыть даташит →LSJ74
✅ Прямая замена📋 Справочный аналог (нет в каталоге)
SST74
✅ Прямая замена📋 Справочный аналог (нет в каталоге)
2SJ74 Максимальные параметры и электрические характеристики
| Device Type | P-Channel JFET (junction type) |
| Drain-Gate Voltage (VGDS) | -25 V |
| Drain Current (ID) | 20 mA |
| Primary Application | Low-noise audio amplifier |
| Recommended Use | First stages of EQ amplifiers and M.C. head amplifiers |
| Корпус | TO-92 (lead formed) |
| Тип монтажа | Through Hole |
| Configuration | Single JFET |
| Channel Type | P-Channel |
| Technology | Silicon junction JFET |
| Grading Ranks | GR, BL (by IDSS range) |
| Lead Finish | Pb (per Mouser 2SJ74-BL listing) |
Конфигурация выводов 2SJ74
| Контакт 1 | S — Source |
| Контакт 2 | G — Gate |
| Контакт 3 | D — Drain |
Типичное применение
2SJ74 подходит для 6 применениеs: Moving-Coil (MC) Phono Head Amplifier, EQ Amplifier First Stage, Microphone Preamplifier Input Buffer, Symmetric / Complementary Low-Noise Input Stage, Instrumentation Front End for Measurement Equipment, Vintage and High-End Audio Restoration.
Moving-Coil (MC) Phono Head Amplifier
The 2SJ74 was explicitly recommended by Toshiba for the first stages of M.C. head amplifiers, where moving-coil cartridge outputs are only fractions of a millivolt and the input device's noise sets the achievable signal-to-noise ratio. Its P-channel JFET topology provides high input impedance and very low equivalent input noise voltage, preserving micro detail on vinyl playback. In practice it operates class-A at a few milliamps with a source degeneration resistor for stability; unlike a bipolar input it contributes negligible input current noise, at the trade-off of lower transconductance per milliamp, which is why IDSS rank matching matters for optimal noise matching to the cartridge source impedance.
Рекомендуется
EQ Amplifier First Stage
Toshiba's datasheet recommends the 2SJ74 specifically for the first stage of EQ (RIAA equalization) amplifiers. In this role the JFET converts the cartridge's tiny signal to a usable level before the frequency-dependent RIAA network, so any input-referred noise is amplified by the full gain of the stage and cannot be removed later. The 25 V drain-gate rating comfortably covers typical preamplifier rails, and the 20 mA rating allows generous class-A idle current for linearity. Designers typically run the device at 2 to 6 mA with a cascode or current-source load; the GR rank is often chosen here for moderate IDSS and easier biasing at low currents.
Рекомендуется
Microphone Preamplifier Input Buffer
Condenser and ribbon microphone signals share the same microvolt-scale sensitivity as phono signals, making the 2SJ74's low input noise and high gate impedance valuable at the front of microphone preamplifiers. The JFET's negligible gate current avoids loading high-impedance microphone sources, and its P-channel polarity lets designers build complementary stages with the 2SK170 for canceling even-order distortion. Typical usage places the 2SJ74 as a source follower or common-source gain device biased at a few milliamps. The trade-off versus modern integrated preamps is discrete bias adjustment, but the noise floor achievable with matched 2SJ74 pairs remains competitive with dedicated low-noise audio ICs.
Рекомендуется
Symmetric / Complementary Low-Noise Input Stage
Classic high-end audio designs pair the P-channel 2SJ74 with the N-channel 2SK170 to form symmetric input stages in which the opposite-polarity devices cancel even-order harmonic distortion and compensate temperature drift. This complementary architecture, popularized by 1980s-2000s amplifier designs, relies on both parts sharing similar noise and transconductance characteristics. The 25 V and 20 mA ratings of the 2SJ74 align with the 2SK170's ratings, allowing identical bias currents in each half. Because IDSS varies part-to-part, production-grade designs select or grade pairs for matched current at a fixed gate-source voltage; the Toshiba GR/BL rank system was designed to support exactly this selection process.
Рекомендуется
Instrumentation Front End for Measurement Equipment
Beyond consumer audio, the 2SJ74 serves as an input device in low-level measurement front ends - bridge amplifier preamps, hydrophone and vibration sensor buffers - where source impedances are high and signals are small. The JFET's near-zero gate input current eliminates the input current noise and bias-current-induced offset errors that plague bipolar inputs, while the 25 V rating supports higher-voltage analog supply rails than many modern low-voltage JFETs permit. Its TO-92 through-hole package also aids manual prototyping and repair of legacy test gear. When original Toshiba stock is exhausted, the Linear Systems LSJ74 continues this application with current-production traceability and equivalent noise specifications.
Рекомендуется
Vintage and High-End Audio Restoration
Servicing 1980s-2000s high-end phono stages, preamplifiers, and head amplifiers frequently requires replacing failed or noisy 2SJ74 devices with genuine originals to preserve the circuit's calibrated bias points and sonic character. Because the 2SJ74 footprint and pinout are unique to this Toshiba family, restoration technicians prefer authentic GR or BL rank stock from legacy distributors such as Mouser over unverified marketplace parts, which the market has shown to include counterfeit TO-92 pieces. When genuine parts are unavailable, the Linear Systems LSJ74 provides a pin-compatible substitute; the technician should then re-verify quiescent current since LSJ74 IDSS grading differs slightly from Toshiba ranks.
Рекомендуется
Сводка рекомендуемых товаров
Справочные инженерные данные для 2SJ74 — сравнение, рекомендации по проектированию и информация о соответствии.
Руководство по выбору
Сравнение с аналогами
| Параметр | Этот товар | 2SJ74-BL | 2SJ74-GR | LSJ74 | SST74 |
|---|---|---|---|---|---|
| Package | TO-92 | 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 | P-Channel |
| Drain-Gate Voltage | -25 V | -25 V | -25 V | -25 V (per Linear Systems replacement spec) | -25 V (per Linear Systems replacement spec) |
| Lifecycle Status | EOL (discontinued) | EOL, residual distributor stock | EOL, residual stock | Active (current production) | Active (current production) |
| Designated Application | Low-noise audio amplifier, EQ first stage, MC head amp | Same (identical die) | Same (identical die) | Ultra-low-noise audio/acoustic applications (direct replacement) | Ultra-low-noise audio/acoustic applications (direct replacement) |
Ключевые отличия
- Factory IDSS grading into GR and BL ranks (против LSJ74)
- Current production availability (против 2SJ74-BL)
- Documented direct-replacement status (против SST74)
Заметки по проектированию
IDSS of the 2SJ74 varies widely both between ranks (GR vs BL) and between units of the same rank. Never assume a nominal current: measure the actual IDSS of each device, or purchase matched pairs, before finalizing the bias network of a first stage. Switching from a GR-rank device to BL without recalculating the source resistor can double the stage current and shift the operating point out of its low-noise region. This is the single most common failure mode when substituting any 2SJ74-class JFET.
Estimated: to keep junction temperature low in a class-A input stage, limit dissipation to a few tens of milliwatts - for example 4 mA at 8 V across the device is about 32 mW, well within any small-signal TO-92 limit. Larger VDS-x-ID products mainly degrade long-term drift rather than cause immediate failure. Provide thermal relief in the bias design by keeping drain-gate voltage well below the 25 V maximum with margin for supply transients.
In through-hole TO-92 audio first stages, keep the gate connection trace as short and guarded as practical: the JFET's high input impedance means PCB leakage and flux residue dominate input noise and offset drift. Clean flux thoroughly after soldering and, in phono applications, consider a gate ring guard driven by the source potential. Lead length also adds inductance only marginally at audio, so mechanical strain relief matters more than length here.
Информация о соответствии
Mouser listing for 2SJ74-BL indicates Pb (lead) lead finish, i.e. legacy pre-RoHS construction. Original part predates modern compliance declarations; no active Toshiba compliance certificate exists for this discontinued device.
