lt5554 Linear Technology Corporation, lt5554 Datasheet - Page 16

• Manufacturer Part Number: lt5554
• Description: Broadband Ultra Low Distortion 7-bit Digitally Controlled Vga
• Manufacturer: Linear Technology Corporation

DEFINITION OF SPECIFICATIONS
LT5554
Amplifi er Impedance and Gain Defi nitions
(Differential)
R
R
C
R
C
R
C
R
C
G
16
IN
O
LOAD
OUT
S
IN
O
LOAD
OUT
M
Input source resistor. Input matching is assumed:
R
LT5554 input resistance (internal, 50Ω)
LT5554 input capacitance (internal)
LT5554 output resistance (internal, 400Ω)
LT5554 output capacitance (internal)
Load resistance as seen by LT5554
output pins
Load capacitance as seen by LT5554
output pins
Total output resistance at LT5554 open-collec-
tors outputs (used in G
R
Total output capacitance at LT5554 output
(used in gain calculation):
C
LT5554 differential transconductance:
G =
OUT
S
OUT
M
= R
= C
= R
IN
I
OUT
V
IN
LOAD
O
|| R
+ C
LOAD
I
OUT
IDC
O
= G
M
Figure 2. Output Equivalent Circuit and Impedance Defi nitions
• V
V,
1.9pF
IN
G
C
O
P
gain calculation):
R
OUT
400Ω
R
O
INTERNAL
400Ω
R
O
OUT
OUT
+
–
R
G
G
P
P
R
LOAD
EXTERNAL
LOAD
IN
OUT
V
P
R
OUT
LT5554 differential voltage gain:
LT5554 differential power gain:
G
Power available at LT5554 input, R
50Ω input matching:
Total power delivered by LT5554 open-collec-
tor outputs:
P
P
G
V is peak value
V
IN
OUT
P
IN
OUT
V
= 10log(R
=
=
10
=
20
is peak value
C
10
LOAD
log
log
log
⎛
⎜
⎜
⎜
⎜
⎜
⎝
⎛
⎝ ⎜
-
V
OUT
IN
(
V
⎛
⎜
⎜
⎜
⎜
⎜
⎝
-
R
V
OUT
(
= I
⎛
⎜
⎝
• G
IN
IN
R
5554 F02
OUT
V
⎛
⎜
⎝
OUT
•
IN
M
2
⎞
⎠ ⎟
V
1
• R
mW
2
2
OUT
=
2
OUT
• R
⎞
⎟
⎠
•
20
1
mW
2
)
OUT
log
⎞
⎟
⎟
⎟
⎟
⎟
⎠
⎞
⎟
⎠
in dBm
)
) in dB
(
⎞
⎟
⎟
⎟ ⎟
⎟
⎟
⎠
G
M
in dBm
•
S
R
,
OUT
= R
,
IN
)
in dB
=
5554f