Texas Instruments THS3121CDR

Overview

THS3121CDR from Texas Instruments is a current-feedback operational amplifier optimized for high-speed video distribution, delivering 120 MHz small-signal bandwidth (G = 2, RL = 50 Ω), 1700 V/μs slew rate, 475 mA output current drive, and <0.007% differential gain error at NTSC/PAL video levels with ±15 V supplies.

For engineers reviewing the THS3121CDR datasheet, THS3121CDR pinout, THS3121CDR application, or THS3121CDR equivalent, this page provides verified pin functions, video-optimized AC performance metrics, thermal design guidance for SOIC-8 PowerPAD™ packaging, and validated alternatives for video driver and capacitive-load driving use cases.

Technical Context

The THS3121CDR employs a current-feedback architecture enabling wide bandwidth independent of closed-loop gain, supporting stable operation up to 120 MHz at G = 2 with 50 Ω loads. Its transimpedance gain of 1.9 MΩ (±15 V) and low 2.5 nV/√Hz input voltage noise ensure high-fidelity signal amplification in analog video paths.

Designed for ±5 V to ±15 V dual-supply operation, it maintains 90 MHz 0.1-dB flat bandwidth and delivers ±13.5 V output swing into 50 Ω while sourcing/sinking ≥400 mA across temperature. The device lacks power-down functionality-distinguishing it from the THS3120 variant-and uses a fixed SOIC-8 (D) package with exposed thermal pad.

Key Specifications

Pinout & Package

THS3121CDR uses an 8-pin SOIC (D) package with PowerPAD™ thermal enhancement. The exposed pad must be soldered to a copper plane for thermal management per TI SLMA002 guidelines. Pin 1 is top-left corner (notch-mark side), with NC pins electrically isolated.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar high-speed current-feedback amplifier applications.

Compared with THS3121IDR, THS3121CDR offers identical video performance at lower cost for commercial environments, while THS3201DR trades output drive for bandwidth and voltage flexibility-making it unsuitable as a drop-in replacement for multi-line video distribution.

Availability

THS3121CDR is available at Aetrix Electronics and suitable for video distribution amplifiers, capacitive load drivers, and high-speed pin drivers requiring stable component supply across industrial and broadcast equipment manufacturing cycles.

Supply support for THS3121CDR includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Texas Instruments is a global semiconductor leader specializing in analog and embedded processing technologies, with decades of expertise in high-speed amplifier design and video signal conditioning.

The THS3121CDR belongs to TI's THS312x current-feedback op-amp family, engineered specifically for demanding analog video, test equipment, and high-current buffer applications requiring wide bandwidth and robust output drive.

FAQ

What is the maximum safe operating junction temperature for THS3121CDR?

The THS3121CDR has a maximum continuous operating junction temperature of +125°C. Exceeding this limit may cause permanent degradation in parameters such as offset voltage drift or output current capability. Thermal design must ensure the PowerPAD™ is soldered to a sufficient copper area, as specified in TI Technical Brief SLMA002, to maintain TJ ≤ +125°C under worst-case load and ambient conditions. Always verify junction temperature using θJA = 95°C/W and measured power dissipation in your layout.

Does THS3121CDR include a power-down feature like THS3120?

No, THS3121CDR does not include a power-down (PD) pin or related functionality. It is a fixed-enable device with typical quiescent current of 7 mA at ±15 V. In contrast, THS3120CDR integrates a PD pin that reduces quiescent current to ~300 μA when asserted. If low-power standby mode is required, THS3120CDR or THS3120IDR must be selected instead of THS3121CDR.

Can THS3121CDR drive 75 Ω video loads directly without external components?

Yes, THS3121CDR is designed to drive 75 Ω video loads directly. With ±15 V supplies, it delivers ±13.5 V output swing into 50 Ω and maintains <0.007% differential gain error across up to eight 150 Ω loads (equivalent to four 75 Ω lines). For optimal video fidelity, use matched 649 Ω feedback resistors and maintain tight layout symmetry on VIN+ and VIN− traces to preserve common-mode rejection.

What is the recommended RISO value when driving 50 pF capacitive load with THS3121CDR?

For a 50 pF capacitive load, the recommended RISO (series isolation resistor) is 30 Ω, per Figure 8 in the THS3121 datasheet (SLOS420E). This value stabilizes the amplifier's phase margin while preserving >100 MHz bandwidth and <12 ns 0.1% settling time. Place RISO as close as possible to the VOUT pin, and avoid routing the output trace past noisy digital signals to prevent coupling into the high-impedance feedback node.

How does THS3121CDR's differential phase performance compare between NTSC and PAL standards?

At ±15 V supply and G = 2, THS3121CDR achieves 0.018° differential phase error for NTSC and 0.022° for PAL, both measured at 40 IRE with worst-case ±100 IRE ramp input. These values meet or exceed broadcast-grade requirements (typically <0.1°), confirming suitability for professional video equipment where color timing accuracy is critical across both analog TV standards.