LMH6555EVAL National Semiconductor, LMH6555EVAL Datasheet - Page 11

• Manufacturer Part Number: LMH6555EVAL
• Manufacturer: National Semiconductor

Specifications of LMH6555EVAL

• Lead Free Status / Rohs Status: Not Compliant

CIRCUIT ANALYSIS
Figure 2 shows the block diagram of the LMH6555.
R
R
R
I
The differential input stage consists of cross-coupled com-
mon base bipolar NPN stages, Q1 and Q2. These stages give
the device its differential input characteristic. The internal loop
gain from V
the output is large, such that these nodes act as a virtual
ground. The cross-coupling will ensure that these nodes are
at the same voltage as long as the amplifier is operating within
its normal range. Output common mode voltage is enforced
CQ1
G1
E1
F1
= R
= R
= R
= I
CQ2
E2
F2
G2
= R
= R
= R
= 12.6 mA
F
E
G
x
= 430Ω
= 25Ω
= 39Ω
and V
y
internal nodes (Q1 and Q2 emitters) to
FIGURE 2. Block Diagram
11
through the action of “A
mode to the “V
The discussion that follows, provides the formulas need-
ed to analyze single ended and differential input applica-
tions. For a more detailed explanation including deriva-
tions, please see the Appendix at the end of the
datasheet.
CM_REF
” input voltage.
CM
” which servos the output common
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