NBB-301 RFMD [RF Micro Devices], NBB-301 Datasheet - Page 4

• Manufacturer Part Number: NBB-301
• Description: Bias Scheme for NBB-Series Amplifiers
• Manufacturer: RFMD [RF Micro Devices]

15
Equation 5 may be substituted into Equation 1 and solved for I
Equation 6 may be differentiated with respect to temperature to get an expression which is useful to observe the effect of
the bias resistor (and supply voltage) selected by the user:
For example, an NBB-400 biased from a 5V supply (V
change with respect to temperature,
which translates into a variation of 14mA over the temperature range from -40°C to +85°C. By comparison, if a 12V sup-
ply rail is with a 162
translates into a current variation of only 2.2mA over the same operating temperature range.
15-26
AN0014
I CC
----------- -
----------- -
I
I
CC
CC
T
T
=
=
=
V
----------------------------------------------------------- -
CC
--------------------------------------
R
------------------- -
–
22
BIAS
R
–
–
BIAS
2.8
–
+




--------- -
bias resistor, then a change in current with respect to temperature reduces to 0.016mA/°C. This
4
--------- -
+
V
T
V
D
+
T


D
=


----------- -




I
V
----------- -
CC
0.108mA
I
D
V
CC
T T


D
–


Copyright 1997-2002 RF Micro Devices, Inc.
O
C
CC
) using a 22
CC
to get:
resistor (R
CC
) will exhibit the following current
Eq. 6
Eq. 7
Eq. 8