LTC6360CMS8E#PBF Linear Technology, LTC6360CMS8E#PBF Datasheet - Page 12

• Manufacturer Part Number: LTC6360CMS8E#PBF
• Manufacturer: Linear Technology

Specifications of LTC6360CMS8E#PBF

• Lead Free Status / Rohs Status: Supplier Unconfirmed

Amplifier Characteristics
Figure 5 shows a simplified schematic of the LTC6360’s
amplifier. The input stage has NPN and PNP differential
pairs operating in parallel. This topology allows the inputs
to swing all the way from the negative rail to within 0.75V
of the positive supply rail. The PNP differential pair is
the primary input differential pair and is active when the
common mode voltage is less than 1.5V from the positive
rail. When the common mode voltage exceeds V
the NPN pair is activated and the PNP is deactivated. The
input stage transconductance, gm, is maintained nearly
constant during the handover from PNP pair to NPN pair.
Additionally, a precision two-point trim algorithm is used
to maintain near constant offset voltage over the entire
input common mode range.
Input bias current flows out of the +IN and –IN inputs. The
magnitude of this current is regulated via an input current
compensation circuit which eliminates the discontinuity
and polarity reversal of input bias current that would oth-
LTC6360
applicaTions inForMaTion
12
+IN
–IN
DESD1
DESD3
V
V
CC
CC
DESD2
DESD4
D1
COMPENSATION
D2
CURRENT
INPUT
Figure 5. Amplifier Simplified Schematic
CC
– 1.5V,
INPUT PAIR
CONTROL
erwise occur when transitioning from one input pair to the
other. Typical total change in input bias current over the
entire input common mode range is approximately 3.5µA.
Amplifier Feedback Components
When feedback resistors are used to set gain, care should
be taken to ensure that the pole formed by the feedback
resistors and the total capacitance at the inverting input,
–IN, does not degrade stability. For instance, to set the
LTC6360 in a gain of +2, R
set to 2k. If the total capacitance at –IN (LTC6360 plus
PC board) were 2pF, a new pole would be formed in the
loop response at 80MHz, which could lead to instability or
ringing in the step response. A capacitor connected across
the feedback resistor and having the same value as the
total –IN parasitic capacitance will eliminate any ringing
or oscillation. Special care should be taken during layout,
including using the shortest possible trace lengths and
removing the ground plane under the –IN pin, to minimize
the parasitic capacitance.
F
DIFFERENTIAL
GENERATOR
and R
DRIVE
G
of Figure 3 could be
V
CC
6360 F05
DESD5
DESD6
V
OUT
CPI
CC
6360f