Bias circuit and power amplifier for improving linearity
A bias circuit includes a current source to generate a reference current, a temperature compensation portion in an off-state in an initial start period in response to a first control signal, and in an on-state in a normal driving period, subsequent to the initial start period, and to receive a first current of the reference current, and a bias output portion to generate a warm up current based on the reference current in the initial start period and to generate a bias current based on a second current, which is lower than the reference current by an amount of the first current, in the normal driving period.
1. A bias circuit, comprising:
a current source configured to generate a reference current;
a temperature compensation portion configured to be in an off-state in an initial start period in response to a first control signal, and to be in an on-state in a normal driving period, subsequent to the initial start period, and to receive a first current lower than the reference current; and
a bias output portion configured to receive the reference current and to generate a warm up current based on the reference current in the initial start period, and to receive a second current, which is lower than the reference current by an amount of the first current, and to generate a bias current based on the second current in the normal driving period,
wherein the temperature compensation portion comprises:
a temperature compensation circuit connected between a first node, an output stage of the current source, and a first ground; and
a first switch connected between the first node and the temperature compensation circuit, and configured to be in an off-state in the initial start period in response to the first control signal and to be in an on-state in the normal driving period, and
wherein the bias output portion comprises:
a bias output circuit connected between the first node and a power amplifier circuit; and
a second switch connected between the first node and the bias output circuit, and configured to be in an on-state in the initial start period and in the normal driving period in response to a second control signal.
2. The bias circuit of claim 1 , wherein the bias output circuit comprises a bias transistor including a base connected to the second switch, a collector connected to an operational voltage terminal, and an emitter connected to the power amplifier circuit, the bias transistor configured to generate the warm up current in the initial start period and to generate the bias current in the normal driving period by amplifying a current input through the second switch, and to output the amplified current to an input node of the power amplifier circuit.
3. The bias circuit of claim 1 , wherein the first current is input in the temperature compensation circuit in the normal driving period and the second current is input in the bias output circuit in the normal driving period, and the first current is higher than the second current.
4. A power amplifier, comprising:
a bias circuit configured to generate a warm up current in an initial start period, and to generate a bias current in a normal driving period, subsequent to the initial start period; and
a power amplifier circuit configured to be warmed up by receiving the warm up current, and to be driven by receiving the bias current,
wherein the bias circuit comprises:
a current source configured to generate a reference voltage;
a temperature compensation portion configured to be in an off-state in the initial start period and to be in an on-state in the normal driving period, and to receive a first current lower than the reference current; and
a bias output portion configured to receive the reference current and to generate the warm up current based on the reference current in the initial start period, and to receive a second current, which is lower than the reference current by an amount of the first current, and to generate the bias current based on the second current in the normal driving period,
wherein the temperature compensation portion comprises:
a temperature compensation circuit connected between a first node, an output stage of the current source, and a first ground; and
a first switch connected between the first node and the temperature compensation circuit, and configured to be in an off-state in the initial start period in response to a first control signal and to be in an on-state in the normal driving period, and
wherein the bias output portion comprises:
a bias output circuit connected between the first node and the power amplifier circuit; and
a second switch connected between the first node and the bias output circuit, and configured to be in an on-state in the initial start period and in the normal driving period in response to a second control signal.
5. The power amplifier of claim 4 , wherein the bias output circuit comprises a bias transistor including a base connected to the second switch, a collector connected to an operational voltage terminal, and an emitter connected to the power amplifier circuit, the bias transistor configured to generate the warm up current in the initial start period and to generate the bias current in the normal driving period by amplifying a current input through the second switch, and to output the amplified current to an input node of the power amplifier circuit.
6. The power amplifier of claim 4 , further comprising a control circuit configured to output the first control signal based on a system enable signal, the first control signal having a switching-on level in the initial start period, and configured to generate the second control signal, the second control signal having a switching-off level in the initial start period and a switching-on level in the normal driving period.
7. The power amplifier of claim 6 , wherein the control circuit comprises:
a buffer configured to output a second control voltage based on the system enable signal;
a constant current source configured to generate a constant current;
a capacitor circuit configured to charge an electric charge based on the constant current and to output a charging voltage; and
a comparator configured to compare the charging voltage and a reference voltage and to output the first control signal having a level depending on a result of the comparison.
8. The power amplifier of claim 6 , wherein the control circuit comprises:
a first constant current source configured to generate a first constant current;
a second constant current source configured to generate a second constant current;
a first capacitor circuit configured to charge an electric charge based on the first constant current and to output a first charging voltage;
a second capacitor circuit configured to charge an electric charge based on the second constant current and to output a second charging voltage;
a discharge control circuit configured to compare the first charging voltage and a first reference voltage and to control an output shutdown and a discharge of the first constant current source and the second constant current source having a level depending on a result of the comparison of the first charging voltage and the first reference voltage;
a discharge circuit configured to discharge the first capacitor circuit and the second capacitor circuit in response to a control of the discharge control circuit;
a first comparison circuit configured to compare the first charging voltage and a second reference voltage and to output the first control signal having a level depending on a result of the comparison of the first charging voltage and the second reference voltage; and
a second comparison circuit configured to compare the second charging voltage and the second reference voltage and to output the second control signal having a level depending on a result of the comparison of the second charging voltage and the second reference voltage.
9. A bias circuit, comprising:
a current source configured to generate a reference current;
a temperature compensation portion configured to be in an off-state in an initial start period in response to a first control signal, and to be in an on-state in a normal driving period, subsequent to the initial start period, and to receive a first current of the reference current; and
a bias output portion configured to generate a warm up current based on the reference current in the initial start period, and to generate a bias current based on a second current, which is lower than the reference current by an amount of the first current, in the normal driving period,
wherein the temperature compensation portion comprises:
a temperature compensation circuit connected between a first node, an output stage of the current source, and a first ground; and
a first switch connected between the temperature compensation circuit and the first ground, and configured to be in an off-state in the initial start period in response to the first control signal and to be in an on-state in the normal driving period, and
wherein the bias output portion comprises:
a bias output circuit connected between the first node and a power amplifier circuit; and
a second switch connected between the bias output circuit and the power amplifier circuit, and configured to be in an on-state in the initial start period and in the normal driving period in response to a second control signal.