LMH6642, LMH6643, LMH6644
www.ti.com
SNOS966P –MAY 2001–REVISED MARCH 2013
APPLICATION INFORMATION
CIRCUIT DESCRIPTION
The LMH664X family is based on proprietary VIP10 dielectrically isolated bipolar process.
This device family architecture features the following:
•
•
•
Complimentary bipolar devices with exceptionally high ft (∼8GHz) even under low supply voltage (2.7V) and
low bias current.
A class A-B “turn-around” stage with improved noise, offset, and reduced power dissipation compared to
similar speed devices (patent pending).
Common Emitter push-push output stage capable of 75mA output current (at 0.5V from the supply rails) while
consuming only 2.7mA of total supply current per channel. This architecture allows output to reach within
milli-volts of either supply rail.
•
•
Consistent performance over the entire operating supply voltage range with little variation for the most
important specifications (e.g. BW, SR, IOUT, etc.)
Significant power saving (∼40%) compared to competitive devices on the market with similar performance.
Application Hints
This Op Amp family is a drop-in replacement for the AD805X family of high speed Op Amps in most applications.
In addition, the LMH664X will typically save about 40% on power dissipation, due to lower supply current, when
compared to competition. All AD805X family’s guaranteed parameters are included in the list of LMH664X
guaranteed specifications in order to ensure equal or better level of performance. However, as in most high
performance parts, due to subtleties of applications, it is strongly recommended that the performance of the part
to be evaluated is tested under actual operating conditions to ensure full compliance to all specifications.
With 3V supplies and a common mode input voltage range that extends 0.5V below V−, the LMH664X find
applications in low voltage/low power applications. Even with 3V supplies, the −3dB BW (@ AV = +1) is typically
115MHz with a tested limit of 80MHz. Production testing guarantees that process variations with not compromise
speed. High frequency response is exceptionally stable confining the typical −3dB BW over the industrial
temperature range to ±2.5%.
As can be seen from the typical performance plots, the LMH664X output current capability (∼75mA) is enhanced
compared to AD805X. This enhancement, increases the output load range, adding to the LMH664X’s versatility.
Because of the LMH664X’s high output current capability attention should be given to device junction
temperature in order not to exceed the Absolute Maximum Rating.
This device family was designed to avoid output phase reversal. With input overdrive, the output is kept near
supply rail (or as closed to it as mandated by the closed loop gain setting and the input voltage). See Figure 60:
Input
Output
+
V
-
V
V
A
= ±2.5V
= +1
S
V
1V/DIV
200 ns/DIV
Figure 60. Input and Output Shown with CMVR Exceeded
However, if the input voltage range of −0.5V to 1V from V+ is exceeded by more than a diode drop, the internal
ESD protection diodes will start to conduct. The current in the diodes should be kept at or below 10mA.
Output overdrive recovery time is less than 100ns as can be seen from Figure 61 plot:
Copyright © 2001–2013, Texas Instruments Incorporated
Submit Documentation Feedback
17
Product Folder Links: LMH6642 LMH6643 LMH6644
TI [ TEXAS INSTRUMENTS ]
