Transconductance stage arrangement
View Patent ↗The present invention relates to a voltage-to-current transconductance stage arrangement comprising a single-ended input, an emitter-coupled pair of transistors, comprising a first transistor and a second transistor, the emitter of a third transistor, being connected to the collector of said first transistor, and differential output. It further comprises at least one common-collector transistor comprising a fourth transistor connected to the base of said second transistor preferably or optionally also and a fifth transistor connected to the base of said third transistor. The size of said fourth, or fourth and fifth transistors considerably exceed the sizes of said second and third transistors. They are biased at ‘off-state’. An extra inductor at the collector of the transistor may be applied to further increase linearity.
1. A voltage-to-current transconductance stage arrangement comprising a single-ended input, an emitter-coupled pair of transistors, comprising a first transistor and a second transistor, the emitter of a third transistor, being connected to the collector of said first transistor, and a differential output, wherein it further comprises a common-collector transistor comprising a fourth transistor connected to the base of said second transistor and in that the size of said fourth considerably exceeds the sizes of said second and third transistors.
2. A transconductance stage arrangement according to claim 1 , wherein the fourth transistor further is connected to the emitter of the third transistor and preferably to the collector of the first transistor.
3. A transconductance stage arrangement according to claim 1 , further comprising a fifth transistor connected to the base of said third transistor.
4. A transconductance stage arrangement according to claim 1 , wherein the emitter size of said fourth or fourth and fifth transistor respectively considerably exceeds the emitter size of said second and third transistors.
5. A transconductance stage arrangement according to claim 4 , wherein the emitter size of said fourth or fourth and fifth transistor respectively is about, or up to, N×the emitter size of the second and/or third transistor, where N is much less than 10.
6. A transconductance stage arrangement according to claim 4 , wherein the emitter size of said fourth or fourth and fifth transistor respectively is more than N×the emitter size of said second and/or third transistor respectively, where N is greater than 10.
7. A transconductance stage arrangement according to claim 1 wherein the collector currents of said fourth (4) or fourth and fifth transistors are the base biasing currents of said second and third transistors respectively.
8. A transconductance stage arrangement according to claim 1 , wherein the collector currents of said fourth or fourth and fifth transistors are biased in an off-state of the respective transistor in such way that they are extremely small.
9. A transconductance stage arrangement according to claim 6 , wherein second biasing means are provided for biasing the collector currents of said fourth and/or fifth transistors in such a manner that said collector currents forming the base biasing currents of said second and third transistors become extremely small.
10. A transconductance stage arrangement according to claim 1 , wherein for an increasing input power, the base-emitter voltage of said fourth or fourth and fifth transistors respectively is adapted to decrease rapidly such that the corresponding DC-voltage components of the base-emitter voltages of said second and third transistors increase, hence providing a good linearity also at large RF input power.
11. A transconductance stage arrangement according to claim 1 , wherein said fourth or fourth and fifth transistors is/are arranged to increase the input impedance of said first and/or second and/or third transistors to a desired level.
12. A transconductance stage arrangement according to claim 11 , wherein resistors or inductors are provided at or connected to the emitters of said first and/or second and/or third transistors in order to further increase the input impedance of said transistors.
13. A transconductance stage arrangement according to claim 1 , wherein a load inductor is arranged to load the collector of the fourth transistor.
14. A transconductance stage arrangement according to claim 12 , wherein the fourth transistor comprises a base-collector junction capacitor and in that said capacitor and the load inductor form a tunable series resonator.
15. A transconductance stage arrangement according to claim 14 , wherein the input signal has a frequency ω 0 , and in that the tunable series resonator is adapted to be tuned such that resonance will occur at twice the input frequency, i.e. at 2ω 0 such that the second harmonic of the input signal will be shorted to ground at input.
16. A transconductance stage arrangement according to claim 1 , wherein the transistors are bipolar transistors.
17. A transconductance stage arrangement according to claim 1 , implemented in SiGe or GaAS.
18. A transconductance stage arrangement according to claim 1 , further comprising an integrated circuit (IC).
19. A transconductance stage arrangement according to claim 1 , wherein said fourth transistor or said fourth and fifth transistors is/are in off-state.
20. A mixer comprising a transconductance stage arrangement according to claim 1 .
21. An amplifier comprising a transconductance stage arrangement according to claim 1 .
22. Use of a transconductance stage arrangement according to claim 1 in a component in a wireless communication system.