LMH6624MA Single / Dual Ultra Low Noise Wideband Operational Amplifier

Single/Dual Ultra Low Noise Wideband Operational Amplifier

Features

► Gain bandwidth (LMH6624) 1.5GHz

► Input voltage noise 0.92nV/

► Input offset voltage (limit over temp) 700uV

► Slew rate 350V/µs n Slew rate (AV = 10) 400V/µs

► HD2 @ f = 10MHz, RL = 100Ω −63dBc

► HD3 @ f = 10MHz, RL = 100Ω −80dBc

► Supply voltage range (dual supply) ±2.5V to ±6V

► Supply voltage range (single supply) +5V to +12V

► Improved replacement for the CLC425 (LMH6624)

► Stable for closed loop |AV| ≥ 10

General Description

The LMH6624/LMH6626 offer wide bandwidth (1.5GHz for single, 1.3GHz for dual) with very low input noise (0.92nV/ , 2.3pA/ ) and ultra low dc errors (100µV VOS, ±0.1µV/˚C drift) providing very precise operational amplifiers with wide dynamic range. This enables the user to achieve closed-loop gains of greater than 10, in both inverting and non-inverting configurations.

The LMH6624 (single) and LMH6626’s (dual) traditional voltage feedback topology provide the following benefits: balanced inputs, low offset voltage and offset current, very low offset drift, 81dB open loop gain, 95dB common mode rejection ratio, and 88dB power supply rejection ratio.

The LMH6624/LMH6626 operate from ± 2.5V to ± 6V in dual supply mode and from +5V to +12V in single supply configuration.

LMH6624 is offered in SOT23-5 and SOIC-8 packages. The LMH6626 is offered in SOIC-8 and MSOP-8 packages.

INTRODUCTION

The LMH6624/LMH6626 are very wide gain bandwidth, ultra low noise voltage feedback operational amplifiers. Their excellent performances enable applications such as medical diagnostic ultrasound, magnetic tape & disk storage and fiber-optics to achieve maximum high frequency signal-tonoise ratios. The set of characteristic plots in the "Typical Performance" section illustrates many of the performance trade offs. The following discussion will enable the proper selection of external components to achieve optimum system performance.

BIAS CURRENT CANCELLATION

  To cancel the bias current errors of the non-inverting configuration, the parallel combination of the gain setting (Rg) and feedback (Rf ) resistors should equal the equivalent source resistance (Rseq) as defined in Figure 1. Combining this constraint with the non-inverting gain equation also seen in Figure 1, allows both Rf and Rg to be determined explicitly from the following equations:  R_f = A_VR_seq and R_g = R_f /^(AV-1)

  When driven from a 0Ω source, such as the output of an op amp, the non-inverting input of the LMH6624/LMH6626 should be isolated with at least a 25Ω series resistor

As seen in Figure 2, bias current cancellation is accomplished for the inverting configuration by placing a resistor (Rb) on the non-inverting input equal in value to the resistance seen by the inverting input (Rf ||(Rg+Rs)). Rb should to be no less than 25Ω for optimum LMH6624/LMH6626 performance. A shunt capacitor can minimize the additional noise of R_b.