High linearity, low noise, wide bandwidth amplifier/buffer
View Patent ↗A radio frequency wide band amplifier having a noise that does not exceed a threshold value, and a linearity better than a threshold value. The radio frequency wide band amplifier architecture includes a first stage amplifier and a second stage amplifier. The second stage amplifier includes an input source resistor (R in ) that receives an input voltage signal, a feedback resistor (R fb ) directly connected to the input source resistor, a p-type metal-oxide-semiconductor (PMOS) transistor directly connected to the input source resistor. The PMOS transistor receives an output from the input source resistor. A n-type metal-oxide-semiconductor (NMOS) transistor directly connected to the input source resistor. The NMOS transistor receives an output from the input source resistor. A lumped output resistor (R out ) that receives an output from the feedback resistor, the PMOS transistor, and the NMOS transistor. A terminal of the lumped output impedance is connected to ground.
1. A radio frequency wide band amplifier architecture having a noise that does not exceed a threshold value, and a linearity better than a threshold value, said radio frequency wide band amplifier architecture comprising a first stage amplifier and a second stage amplifier, said second stage amplifier comprising:
an input source resistor (R in ) that receives an input voltage signal;
a feedback resistor (R fb ) directly connected to said input source resistor;
a p-type metal-oxide-semiconductor (PMOS) transistor directly connected to said input source resistor, wherein said PMOS transistor receives an output from said input source resistor;
a n-type metal-oxide-semiconductor (NMOS) transistor directly connected to said input source resistor, wherein said NMOS transistor receives an output from said input source resistor; and
a lumped output resistor (R out ) that receives an output from said feedback resistor, said PMOS transistor, and said NMOS transistor, wherein a terminal of said lumped output resistor is connected to ground,
wherein g m equals a trans-conductance of said PMOS transistor (g mp ) plus a trans-conductance of said NMOS transistor (g mn ), and wherein said g m is determined in accordance with equation: g m =g mp +g mn .
2. The architecture of claim 1 , wherein a gain of said second stage of said radio frequency wide band amplifier architecture is determined in accordance with equation:
Gain
=
(
g
m
-
1
R
fb
)
(
R
fb
//
R
out
)
,
and wherein said g m is a trans-conductance of a MOS transistor of said radio frequency wide band amplifier architecture.
3. The architecture of claim 1 , wherein said threshold value equals 3 dB.
4. The architecture of claim 2 , wherein an input impedance (Z in ) equals R fb divided by (1+Gain) and is determined in accordance with equation:
Z
in
=
R
fb
1
+
Gain
.
5. The architecture of claim 1 , wherein an output impedance (Z out ) is determined in accordance with equation:
Z
out
=
R
out
//
(
R
fb
+
R
in
)
//
(
R
fb
+
R
in
g
m
R
in
)
.
6. The architecture of claim 2 , wherein a square of noise input referred voltage (V 2 noise_input_referred) is determined in accordance with equation:
V
noise_input
_referred
2
=
4
kT
Gain
2
(
1
(
1
+
g
m
R
in
)
+
R
in
+
Rfb
R
out
)
2
[
R
fb
(
1
+
g
m
R
in
)
2
+
γ
g
m
(
R
in
+
R
fb
)
2
]
.
7. The architecture of claim 1 , wherein said lumped output resistor (R out ) receives said output from a drain terminal of said PMOS transistor, and a drain terminal of said NMOS transistor.
8. The architecture of claim 1 , wherein said first stage amplifier achieves a low noise with a high transconductance, and wherein said second stage amplifier provides a noiseless low impedance to limit the swing of the first stage amplifier to achieve high linearity.
9. The architecture of claim 8 , wherein said first stage amplifier comprises any of a n-type metal-oxide semiconductor (NMOS) transistor, a p-type metal-oxide-semiconductor (PMOS) transistor or both that provides high transconductance for low input referred noise.
10. The architecture of claim 9 , wherein said second stage amplifier contributes very little noise compared with the noise of the first stage amplifier and provides a low impedance to the first stage amplifier to limit the swing of the output of the first stage amplifier for the benefit of linearity.
11. A two stage radio frequency wide band amplifier architecture comprising:
a first stage amplifier having a noise that does not exceed a threshold value; and
a second stage amplifier that limits a swing of an output of said first stage amplifier, said second stage amplifier comprising:
a first n-type metal-oxide-semiconductor (NMOS) transistor that receives an input voltage signal from said first stage amplifier;
a p-type metal-oxide-semiconductor (PMOS) transistor directly connected to said first NMOS transistor;
a feedback resistor directly connected to said first NMOS transistor; and
a load resistor that receives an output from said feedback resistor, said first PMOS transistor, and said second NMOS transistor,
wherein a trans-conductance of said PMOS transistor (g mp ) plus a trans-conductance of said NMOS transistor (g mn ) equals g m such that said g m is determined in accordance with equation: g m =g mp +g mn , and
wherein said g m is a trans-conductance of a MOS transistor of said radio frequency wide band amplifier architecture.
12. A method of using a radio frequency wide band amplifier architecture having a noise that does not exceed a threshold value, and a linearity better than a threshold value, said radio frequency wide band amplifier architecture comprising a first stage amplifier and a second stage amplifier, wherein said method comprises:
receiving an input voltage signal in an input source resistor (R in );
directly connecting a feedback resistor (R fb ) to said input source resistor;
receiving an output from said input source resistor into a p-type metal-oxide-semiconductor (PMOS) transistor that is directly connected to said input source resistor;
receiving an output from said input source resistor into a n-type metal-oxide-semiconductor (NMOS) transistor that is directly connected to said input source resistor; and
receiving an output from said feedback resistor, said PMOS transistor, and said NMOS transistor into a lumped output resistor (R out ), wherein a terminal of said lumped output resistor is connected to ground,
wherein g m equals a trans-conductance of said PMOS transistor (g mp ) plus a trans-conductance of said NMOS transistor (g mn ), and wherein said g m is determined in accordance with equation: g m =g mp +g mn .
13. The method of claim 12 , wherein a gain of said second stage of said radio frequency wide band amplifier architecture is determined in accordance with equation:
Gain
=
(
g
m
-
1
R
fb
)
(
R
fb
//
R
out
)
,
and wherein said g m is a trans-conductance of a MOS transistor of said radio frequency wide band amplifier architecture.
14. The method of claim 12 , wherein said threshold value equals 3 dB.
15. The method of claim 13 , wherein an input impedance (Z in ) equals R fb divided by (1+Gain) and is determined in accordance with equation:
Z
in
=
R
fb
1
+
Gain
.
16. The method of claim 12 , wherein an output impedance (Z out ) is determined in accordance with equation:
Z
out
=
R
out
//
(
R
fb
+
R
in
)
//
(
R
fb
+
R
in
g
m
R
in
)
.
17. The method of claim 13 , wherein a square of noise input referred voltage (V 2 noise_input_referred) is determined in accordance with equation:
V
noise_input
_referred
2
=
4
kT
Gain
2
(
1
(
1
+
g
m
R
in
)
+
R
in
+
Rfb
R
out
)
2
[
R
fb
(
1
+
g
m
R
in
)
2
+
γ
g
m
(
R
in
+
R
fb
)
2
]
.
18. The method of claim 12 , wherein said lumped output resistor (R out ) receives said output from a drain terminal of said PMOS transistor, and a drain terminal of said NMOS transistor.
19. The method of claim 12 , wherein said first stage amplifier achieves a low noise with a high transconductance, wherein said second stage amplifier provides a noiseless low impedance to limit the swing of the first stage amplifier to achieve high linearity, wherein said first stage amplifier comprises any of a n-type metal-oxide semiconductor (NMOS) transistor, a p-type metal-oxide-semiconductor (PMOS) transistor or both that provides high transconductance for low input referred noise.
20. The method of claim 19 , wherein said second stage amplifier contributes very little noise compared with the noise of the first stage amplifier and provides a low impedance to the first stage amplifier to limit the swing of the output of the first stage amplifier for the benefit of linearity.