2SJ74-GR/BL - P-Channel Low-Noise Audio JFET | Toshiba
料号： 2SJ74-GR/BL ✓ 量产中| 数量 | 单价 | 小计 |
|---|---|---|
| 1 | $2.5 | $2.50 |
| 10 | $2.25 | $22.50 |
| 100 | $1.98 | $198.00 |
| 500 | $1.75 | $875.00 |
| 1,000 | $1.55 | $1,550.00 |
2SJ74-GR/BL 概述
A JFET (junction field-effect transistor) is a voltage-controlled semiconductor in which the gate-channel junction is reverse-biased, producing an extremely high input impedance and very low gate leakage current. Within the signal-chain hierarchy, the JFET sits alongside bipolar transistors and MOSFETs as a discrete transistor, and it is prized in the front-end tier of audio preamplifiers precisely because its noise current is far lower than that of a bipolar device driving a high-impedance source.
Key features of the 2SJ74 include ultra-low noise figure in the audio band, high transconductance for a small-signal JFET, and tight Idss grading (GR/BL) that simplifies matched-pair selection for differential input stages. According to Toshiba datasheet information, the device is specifically recommended for the first stages of EQ (RIAA) amplifiers and MC (moving-coil) head amplifiers, where the source impedance is high and every microvolt of input noise matters.
Architecturally, the 2SJ74 is the P-channel complement of the famous Toshiba 2SK170 N-channel JFET, and the two are frequently used together in complementary push-pull front ends. The lateral JFET structure yields low 1/f noise corner and stable Idss over time, which is why the part remains a cult favorite in high-end audio despite its discrete, decades-old process.
Typical applications include phono preamplifier input stages, moving-coil step-up head amplifiers, microphone preamp inputs, and low-noise differential pairs in discrete op-amp circuits. Its complementary pairing with the 2SK170 covers most classic Japanese hi-fi front-end topologies.
Designers should bias the device well within its 400 mW package dissipation limit and verify Idss grading before use in matched circuits, since GR and BL grades differ by roughly a factor of two in saturation current.
This page adds value beyond the datasheet by synthesizing distributor sourcing data, verified drop-in alternatives from Linear Systems, grade comparisons, and practical audio design notes in one place.
直接替换替代料： 2SJ74-GR/BL ——相同封装，引脚兼容。需要 PCB 改动的不同封装料号已排除。
本系列中的变体
可与以下型号直接替换的同系列型号： 2SJ74-GR/BL （相同外形与封装尺寸） ——差异在于 Package, Transistor Type, Configuration, Mounting Type, Grade Suffix.
快速对比工具——选择替代料号进行并排对比：
2SJ74-BL
✅ 直接替换✓ 有现货
$2.94 / 个
查看数据手册 →2SJ74-GR
✅ 直接替换✓ 有现货
联系询价
查看数据手册 →LSJ74
✅ 直接替换📋 参考替代料（不在目录中）
SST74
✅ 直接替换📋 参考替代料（不在目录中）
2SJ74-GR/BL 最大额定值与电气特性
| 晶体管类型 | P-Channel JFET |
| Drain-Source Voltage (Vdss) | 25 V |
| Drain Current (Id) | 0.02 A |
| Power Dissipation (Pd) | 400 mW |
| Idss Grade GR | 2.6 mA to 6.5 mA |
| Idss Grade BL | 6 mA to 12 mA |
| Configuration | Single JFET |
| Channel Mode | Depletion |
| 封装 | TO-92 style (Toshiba 2-5F1D / SC-43), 3 PIN |
| 安装类型 | Through Hole |
| Recommended Application | Low noise audio amplifier, EQ amplifier first stage, MC head amplifier |
| Polarity | P-Channel |
| Number of Units in IC | 1 |
2SJ74-GR/BL 引脚配置
| 引脚 1 | S — Source terminal of the P-channel JFET |
| 引脚 2 | G — Gate terminal (reverse-biased control junction) |
| 引脚 3 | D — Drain terminal |
典型应用
2SJ74-GR/BL 适用于 6 应用s: Phono Preamplifier EQ Input Stage, MC Head Amplifier, Discrete Op-Amp / Differential Input Pairs, Microphone Preamplifier Input, Active Current Sources and Cascodes, Instrumentation and Sensor Front Ends.
Phono Preamplifier EQ Input Stage
The 2SJ74-GR/BL is explicitly recommended by Toshiba for the first stages of EQ (RIAA) amplifiers. In a phono preamplifier, the cartridge signal is only a few millivolts, so input-referred voltage noise directly sets the signal-to-noise ratio of the entire playback chain. The 2SJ74's JFET gate draws essentially zero gate current, eliminating bias-current noise into the high-impedance cartridge load, while its high transconductance at 2-6 mA drain current yields sub-nanovolt-per-root-hertz-class voltage noise. GR-grade parts (Idss 2.6-6.5 mA) suit lower-bias RIAA front ends where the cartridge impedance is moderate. Placed as a common-source or cascoded input stage followed by the passive or active RIAA network, the 2SJ74 preserves the microdynamic detail that defines high-end vinyl reproduction.
推荐
MC Head Amplifier
Moving-coil (MC) cartridges output only 0.2-0.5 mV, demanding the lowest-noise input devices available. Toshiba specifically recommends the 2SJ74 for MC head amplifiers, and the BL grade (Idss 6-12 mA) is the usual choice because higher saturation current brings higher transconductance and therefore lower input voltage noise. A typical topology parallels two or three matched 2SJ74-BL devices or cascodes them with a 2SK170 to multiply effective transconductance while keeping input capacitance low enough not to load the cartridge. Running each device at 3-5 mA keeps dissipation far below the 400 mW limit. Because genuine parts are scarce, the Linear Systems LSJ74 with matched Idss bins is the practical sourcing path for new MC head amplifier builds.
推荐
Discrete Op-Amp / Differential Input Pairs
The 2SJ74 excels as the P-channel input pair of discrete operational amplifiers and instrumentation front ends. Its tight Idss grading (GR: 2.6-6.5 mA; BL: 6-12 mA) allows selection of closely matched pairs, typically within 0.5 mA, which minimizes input offset and drift in a differential stage. The extremely low gate leakage of a JFET input - orders of magnitude below bipolar alternatives - makes the stage suitable for high-impedance sources such as pH probes, photodiodes, and capacitor microphones. In complementary designs, 2SJ74/2SK170 pairs form classic Japanese hi-fi input structures combining high input impedance with low noise. Designers should bias each device at 2-5 mA and provide source degeneration resistors to linearize the pair and stabilize gain against Idss spread.
推荐
Microphone Preamplifier Input
Condenser and ribbon microphone preamplifiers benefit from the 2SJ74's combination of ultra-low voltage noise and negligible gate current. For ribbon microphones, whose source impedance is very low (under 1 ohm at the transformer secondary but often several hundred ohms after step-up), voltage noise dominates, and the high-transconductance BL grade biased at 5-6 mA delivers the lowest achievable input noise floor. For condenser inputs, the JFET gate's near-zero leakage preserves the bias network's impedance and prevents noise from polarizing resistors. The 25 V drain-source rating comfortably covers 24 V phantom-power-derived rails, and the TO-92 package dissipates a few tens of milliwatts in these roles with no thermal design effort.
推荐
Active Current Sources and Cascodes
Beyond input stages, the 2SJ74 is widely used as a P-channel JFET current source and cascode element in high-end audio circuits. Connected gate-to-source with a trimming resistor, a BL-grade 2SJ74 supplies a stable 4-10 mA bias current for differential tails and single-ended stages, with the JFET's high output impedance improving power-supply rejection of the fed stage. In cascode configurations, a 2SJ74 stacked on another P-channel JFET multiplies output impedance and linearizes the lower device, a technique popularized in First Watt and Pass Laboratories designs where matched JFET sets are commercially specified. The 25 V rating and 400 mW dissipation limit define the cascode voltage budget and per-device bias ceiling.
推荐
Instrumentation and Sensor Front Ends
High-impedance sensor interfaces - piezoelectric accelerometers, hydrophones, photodiode transimpedance stages, and electrometer inputs - require an input device with femtoampere-class gate current and low flicker noise. The 2SJ74's reverse-biased gate junction provides exactly this, and its GR grade Idss of 2.6-6.5 mA permits low-power biasing where sensor self-heating or supply budget is constrained. In practice the device is arranged as a source follower buffering the sensor into a low-noise gain stage, where the JFET's low voltage noise keeps the buffer from degrading the signal chain noise floor. The through-hole TO-92 package also suits prototyping and low-volume instrument production where hand matching and selection are routine.
推荐
推荐产品汇总
工程参考数据： 2SJ74-GR/BL ——对比、设计指导和合规信息。
选型指南
与替代料对比
| 参数 | 本产品 | 2SJ74-BL | LSJ74 | SST74 |
|---|---|---|---|---|
| Package | TO-92 style (2-5F1D / SC-43) | TO-92 style (2-5F1D / SC-43) - same | TO-92 - same | TO-92 (LSJ/SST74 series) - same package family |
| Brand | Toshiba | Toshiba | Linear Systems | Linear Systems |
| Polarity / Type | P-Channel JFET | P-Channel JFET | P-Channel JFET | P-Channel JFET |
| Idss Range | GR: 2.6-6.5 mA / BL: 6-12 mA | 6-12 mA (BL grade) | Equivalent GR/BL grading bins offered | Equivalent GR/BL grading bins offered |
| Noise Character | Ultra-low noise, audio-optimized | Ultra-low noise, audio-optimized | Ultra-low noise, audio/acoustic per Linear Systems | Ultra-low noise, audio/acoustic per Linear Systems |
| Positioning | Original Toshiba audio JFET, EQ first stage / MC head amp | Higher-Idss grade of the same device | Direct replacement for Toshiba 2SJ74 | Series counterpart of LSJ74 direct replacement |
关键差异点
- Tighter low-current Idss bin available (GR grade) （对比 2SJ74-BL)
- Verified manufacturer-endorsed second source （对比 LSJ74)
- Toshiba-recommended for EQ and MC head amplifier first stages （对比 Generic audio JFETs)
设计说明
Counterfeit 2SJ74 and 2SK170 parts are widespread on secondary marketplaces; many fakes are repackaged lower-grade devices or wrong-polarity transistors. Source only from authorized distributors (e.g., Mouser lists 2SJ74-BL) or the Linear Systems LSJ74 as a verified replacement. Always measure Idss on receipt: GR parts must fall in 2.6-6.5 mA and BL parts in 6-12 mA. A part measuring outside its bin will shift your bias point and can double the offset in matched differential pairs.
Keep static dissipation well below the 400 mW package limit. Estimated: a BL-grade device at Idss = 10 mA across Vds = 12 V dissipates 120 mW, a safe margin, but the same current across 25 V reaches 250 mW - acceptable yet hot for TO-92, and it will shift Idss via self-heating. Budget cascode stacking so no single device sees more than roughly 12-15 V and 150 mW in precision circuits where drift matters.
Match JFETs thermally and electrically in differential stages: select parts within 0.5 mA Idss and mount them physically adjacent (or thermally coupled) so their bias points track with temperature. Use source degeneration (100-500 ohm trimmers) to linearize matched pairs and null offset. Keep the gate node guarded and high-impedance; JFET gate leakage is minuscule but PCB leakage currents can dominate it, so clean flux residue and consider guard rings on the gate trace.
合规信息
Compliance data not present in the provided verified web data. Mouser lists the 2SJ74-BL as 'Pb Small Signal Trans' family; verify RoHS/lead-free status on the current Toshiba product page before specifying in restricted applications.
