Texas Instruments LF398N Sample and Hold Amplifier IC, DIP-8, 1MHz

The Texas Instruments LF398N/NOPB is a high-performance, monolithic sample-and-hold integrated circuit that utilises advanced BI-FET technology. This combination delivers exceptional DC accuracy, rapid signal acquisition, and an extremely low droop rate, making it a cornerstone component for precision analogue signal processing.

Operating as a unity-gain follower, it boasts a typical DC gain accuracy of 0.002% and can acquire a signal to within 0.01% in as little as 6µs. Its design incorporates a bipolar input stage, which achieves a low input offset voltage and provides a wide bandwidth. This bandwidth allows the circuit to be used within the feedback loop of 1MHz operational amplifiers without introducing stability issues.

Key Features & Performance

• Ultra-High Input Impedance: With an input impedance of 10¹⁰Ω, the circuit can interface with high-source impedances without any loss of accuracy.
• Excellent Hold Mode Characteristics: The use of P-channel JFETs in the output amplifier results in very low droop rates, typically as low as 5mV per minute with a 1µF hold capacitor. These JFETs offer lower noise and greater temperature stability compared to MOS devices used in earlier designs.
• Logic Compatibility: The control logic input is fully compatible with TTL, PMOS, and CMOS logic levels, ensuring easy integration into digital control systems.
• Stable Operation: Input characteristics remain consistent when switching between sample and hold modes, and the device maintains a high supply rejection ratio in both states.

Specifications & Handling

• Typical Hold Step: 0.5mV (with 0.01µF capacitor)
• Power Dissipation: 500mW
• Supply Voltage: ±15V (operating range from ±5V to ±18V)
• Package: Standard 8-pin DIP (Dual In-line Package)
• ESD Warning: This device has limited built-in ESD protection. During storage or handling, the IC