CN104113291A - Low-voltage Darlington amplifier - Google Patents

Abstract

The invention discloses a low-voltage Darlington amplifier which comprises a basic Darlington amplifying unit, an alternating-current and direct-current separating unit and a power voltage polarity conversion unit. Alternating current and direct current of the basic Darlington amplifying unit are separated and an alternating current ground is clamped in place. A direct current reference ground of the Darlington amplifier is clamped to a negative reference level, thus potential difference from the power voltage to the direct current reference ground is improved. The power voltage of the conventional Darlington amplifier is higher than 5-7V generally, but the power voltage of the low-voltage Darlington amplifier is 3-4V. The low-voltage Darlington amplifier is widely applied to various Darlington structural circuits of microwave monolithic integrated circuits IC.

Description

Low-voltage darlington amplifier

Technical field

The present invention relates to a kind of darlington amplifier, particularly a kind of low-voltage darlington amplifier, it directly applies to all kinds of Darlington circuits field in microwave monolithic IC.

Background technology

Amplifier is the essential elements in radiofrequency signal treatment system, and its performance has directly determined the performance of radiofrequency signal treatment system.Owing to having, working band is wide, the linearity is high, be easy to the features such as cascade is widely applied for darlington amplifier.

Darlington amplifier, in the time of work, needs the outside bias current providing, and generally realizes by voltage source and external bias resistance.On biasing resistor, voltage drop is larger, and in the time of temperature and change in voltage, the bias current of darlington amplifier is more stable.In order to obtain stable biasing, on biasing resistor, generally need to have the voltage drop of 1～2V at least.In order to obtain good linear power output, darlington amplifier needs higher device terminal voltage, and when this makes darlington amplifier steady operation, required supply voltage is higher.Along with the development of signal processing system, more and more extensive to the demand of circuit low pressure applications, the application of darlington amplifier is restricted.

Automatic biasing darlington amplifier circuit diagram as shown in Figure 1, transistor Q _3a, capacitor C _1a, resistance R _2a, resistance R _5aand resistance R _6aform biasing circuit, for darlington amplifier provides biasing.With traditional darlington amplifier comparison, this scheme has just been eliminated the voltage drop on biasing resistor, and the device terminal voltage of device darlington amplifier itself does not change, so can not solve the higher problem of darlington amplifier device terminal voltage, and because automatic biasing part is connected with circuit signal input, can bring deterioration noise factor, worsen the series of problems such as input voltage standing-wave ratio.

Summary of the invention

For overcoming the higher problem of the required supply voltage of above-mentioned darlington amplifier, the present invention proposes a kind of low-voltage darlington amplifier, by the scheme that uses the conversion of supply voltage polarity and alternating current-direct current split circuit and darlington amplifier to combine, compared with normally working under low supply voltage.

A kind of low-voltage darlington amplifier of the present invention, is characterized in that, it contains:

A basic Darlington amplifying unit, comprises triode Q _1b, triode Q _2b, resistance R _1b, resistance R _2b, resistance R _3b, wherein, Q _1bemitter and Q _2bbase stage be connected, Q _1bcollector electrode and Q _2bcollector electrode be connected, and with output V _outconnect Q _1bbase stage and input V _inconnect R _1ba termination Q _1bbase stage, R _1banother termination output V _out, R _2ba termination Q _1bbase stage, R _3bone end and Q _1bemitter be connected, R _4bone end and Q _2bemitter be connected, R _2bthe other end and R _3bthe other end, resistance R _4bthe other end link together, tie point is A; With

An alternating current-direct current separative element, comprises capacitor C _1b, wherein, C _1bone end be connected with tie point A, C _1bother end ground connection; With

A supply voltage polarization converting unit, comprises metal-oxide-semiconductor M _1b, metal-oxide-semiconductor M _2b, metal-oxide-semiconductor M _3b, metal-oxide-semiconductor M _4b, inverter INV, oscillator OSC, capacitor C _2b, capacitor C _3b, wherein, the output V of OSC _oSCoutwith M ₁grid, M _3bgrid, M _4bgrid, the input V of INV _iNVinlink together, the output V of INV _iNVoutwith M _2bgrid link together, M _4bdrain electrode meet power supply V _cC, M _4bsource electrode and M ₃drain electrode, C _3bone end link together, tie point is B, M _2bsource electrode and M _1bdrain electrode, C _3bthe other end link together, tie point is C, M _1bsource electrode and C _2bone end be connected, tie point is A, M _2bgrounded drain, M _3bsource electrode and capacitor C _2bthe other end link together, and ground connection.

The outside direct current biasing of described low-voltage darlington amplifier, contains:

A biasing resistor R _bias, a choke induction L _chokewith a shunt capacitance C _bypass, wherein, L _chokeone end and low-voltage darlington amplifier output V _oUTconnect L _chokethe other end and R _biasand C _bypassone end be connected, C _bypassother end ground connection, R _biasthe other end be connected with power supply.

Beneficial effect:

Low-voltage darlington amplifier circuit of the present invention comprises a basic Darlington amplifying unit, an alternating current-direct current separative element and a supply voltage polarization converting unit.It has following characteristics:

1. circuit of the present invention is in the reference ground of basic Darlington amplifying unit A point series winding capacitor C _1bbe connected to the ground, form alternating current-direct current separative element, by the interchange of Darlington amplifying unit and direct current separate, and will exchange ground clamper and arrive ground.

2. by metal-oxide-semiconductor M _1b, M _2b, M _3b, M _4b, inverter INV, oscillator OSC, capacitor C _2band C _3bcomposition supply voltage polarity switching output be connected with the reference ground A of basic Darlington amplifying unit, by the direct current of darlington amplifier with reference to ground clamper to negative reference level, thereby improved supply voltage to direct current with reference to the electrical potential difference between ground.

In the situation that ensureing that Darlington amplifying unit device terminal voltage and supply voltage electrical potential difference are constant, reach the object that reduces power supply voltage.Tradition darlington amplifier supply voltage is generally greater than 5～7V, and low-voltage darlington amplifier supply voltage of the present invention can be low to moderate 3～4V.

Due to alternating current-direct current separative element and the supply voltage polarization converting unit of circuit of the present invention, be not connected with circuit signal input, thereby can not affect the electrical characteristics of basic darlington amplifier, avoid the problem such as noise factor, the deterioration of input voltage standing-wave ratio.Automatic biasing darlington amplifier noise factor is generally greater than 5dB, and low-voltage darlington amplifier of the present invention generally to reach be 2～3dB.

Brief description of the drawings

Fig. 1 is automatic biasing darlington amplifier circuit diagram;

Fig. 2 is the circuit diagram of low-voltage darlington amplifier of the present invention.

Embodiment

The circuit diagram of the concrete low-voltage darlington amplifier of implementing of the present invention as shown in Figure 2.It comprises a basic Darlington amplifying unit, an alternating current-direct current separative element and a supply voltage polarization converting unit.Its concrete structure and annexation, interactively are identical with the summary of the invention part of this specification, no longer repeat herein.

The operation principle of circuit of the present invention is as follows:

Radiofrequency signal is passed through V _iNport enters after darlington amplifier, through triode Q _1bwith triode Q _2bafter the Darlington multiple tube of composition amplifies signal, by V _oUTport output.Resistance R _1band resistance R _2bdetermine triode Q _1bbase stage working point, and gain, bandwidth, input impedance and noise etc. to darlington amplifier play an important role, resistance R _4bfor triode Q _1bemitter is followed resistance, has negative feedback, thereby improves triode Q _1bthe stability of quiescent point reduces triode Q simultaneously _1bthe impact of Miller electric capacity on circuit bandwidth, improve the high frequency characteristics of circuit, resistance R _4bfor increasing the load capacity of stabilizing and increasing of circuit.

Capacitor C _1bform alternating current-direct current separative element, by the interchange of darlington amplifier and direct current separate, and will exchange ground clamper and arrive ground.Capacitor C _1bselection relevant with the low-limit frequency of amplifier work, C _1bunder interchange condition, impedance is determined by formula (1), and its absolute value of General Requirements is less than 1.

Z _C＝1/jwC _1b (1)

V _O＝-(V _CC-R _O×I _O) (2)

$R_O\≈\frac{1}{f_{\mathrm{OSC}}\×C_{3b}}+4\×(R_{M1b}+R_{M3b}+{\mathrm{ESR}}_{C3b})+{\mathrm{ESR}}_{C2b}---\left(3\right)$

At known Darlington amplifying unit operating current I _oin situation, the output voltage of supply voltage polarization converting unit can be calculated by (2) formula, V _cCfor supply voltage, from (3) formula, the output impedance R of supply voltage polarization converting unit _oby oscillator output frequency f _oSC, capacitor C _3b, metal-oxide-semiconductor M _1bconducting resistance R _m1b, metal-oxide-semiconductor M _3bconducting resistance R _m3b, capacitor C _2bequivalent series resistance ESR _c2band capacitor C _3bequivalent series resistance ESR _c3bcommon decision.

For avoiding capacitor C _3band capacitor C _2bvalue is excessive, and the operating frequency General Requirements of oscillator OSC is greater than 10KHz.Output square-wave signal V _oSCoutcontrol metal-oxide-semiconductor M _1b, metal-oxide-semiconductor M _3bwith metal-oxide-semiconductor M _4bswitch, square-wave signal is by after inverter INV, obtain one group with the signal V of former square-wave signal single spin-echo _iNVout, signal V _iNVoutcontrol metal-oxide-semiconductor M _2bswitch.Metal-oxide-semiconductor M _1b, metal-oxide-semiconductor M _2b, metal-oxide-semiconductor M _3bwith metal-oxide-semiconductor M _4bsource leak level conducting resistance as far as possible little, meet darlington amplifier work requirements by current capacity.Metal-oxide-semiconductor M _4bfor PMOS pipe, metal-oxide-semiconductor M _1b, metal-oxide-semiconductor M _2bwith metal-oxide-semiconductor M _3bfor NMOS pipe, this is in order to prevent mistake high power loss and the device generation latch up effect of supply voltage polarity switching in the time starting working.

At the front half period of oscillator OSC output square-wave signal, metal-oxide-semiconductor M _1b, metal-oxide-semiconductor M _3bturn-off metal-oxide-semiconductor M _2b, metal-oxide-semiconductor M _4bconducting, capacitor C _3btwo ends by power source charges to supply voltage V _cC, rear half period, metal-oxide-semiconductor M _1b, metal-oxide-semiconductor M _3bconducting, metal-oxide-semiconductor M _2b, metal-oxide-semiconductor M _4bturn-off, by capacitor C _3bgive capacitor C _2bcharging, metal-oxide-semiconductor M under conduction status _3binternal resistance between the leakage of source is ignored, because B point is now clamped to ground, capacitor C _2bother end A, can obtain voltage V _o, be clamped to V the direct current of darlington amplifier now _o.

$V_{O\left(\mathrm{ripple}\right)}=\frac{I_O}{f_{\mathrm{OSC}}\×C_{2b}}+2{\×I}_O\×{\mathrm{ESR}}_{C2b}---\left(4\right)$

The fluctuation of supply voltage polarity switching output voltage is definite by (4) formula, and General Requirements is less than 0.2V.Capacitor C _3band capacitor C _2bcapacitance is larger, generally adopts external form, capacitor C _3bvalue generally need be more than or equal to capacitor C _2bvalue.Capacitor C _2band capacitor C _3bconventional value is as shown in table 1.

Table 1 capacitor C ₂and capacitor C ₃value

f OSC(kHz)	V CC(V)	I O(mA)	C 2b(μF)	C 3b(μF)
					20	5	50	10	10
50	5	50	3.3	3.3
					250	5	50	1	1

By alternating current-direct current separative element, low-voltage darlington amplifier is exchanged with reference to ground constant, ensure that Darlington amplifying unit radiofrequency characteristics does not change.Obtain negative reference level by supply voltage polarity switching, by the direct current of darlington amplifier with reference to ground clamper to negative reference level, ensureing that supply voltage and low-voltage darlington amplifier direct current are poor constant in the situation that with reference to earth potential, can reach the object of reduction power supply voltage.

Manufacturing process of the present invention is general SiGe 0.35 μ m BiCMOS technique.

PMOS, NMOS pipe in circuit of the present invention and the basic parameter of BJT pipe are:

Gate oxide thickness 7.2 nm～8.4 nm of NMOS pipe;

Gate oxide thickness 7.0 nm～8.2 nm of PMOS pipe

The V of BJT pipe _ceoit is the high-voltage power bipolar transistor of 6 V

M _1b, M _2b, M _3b, M _4bgrid long: 0.35 μ m;

M _1b, M _2b, M _3b, M _4bgrid width: 250 μ m;

Resistance R _1b, R _2b, R _3b, R _4bbe the polysilicon negative resistance with negative temperature coefficient.Their parameter is respectively:

R _1bresistance is 500 Ω;

R _2bresistance is 500 Ω;

R _3bresistance is 154 Ω;

R _4bresistance is 11 Ω.

Claims (2)

1. a low-voltage darlington amplifier, is characterized in that, it contains:

A basic Darlington amplifying unit, comprises triode Q _1b, triode Q _2b, resistance R _1b, resistance R _2b, resistance R _3b, wherein, Q _1bemitter and Q _2bbase stage be connected, Q _1bcollector electrode and Q _2bcollector electrode be connected, and with output V _outconnect Q _1bbase stage and input V _inconnect R _1ba termination Q _1bbase stage, R _1banother termination output V _out, R _2ba termination Q _1bbase stage, R _3bone end and Q _1bemitter be connected, R _4bone end and Q _2bemitter be connected, R _2bthe other end and R _3bthe other end, resistance R _4bthe other end link together, tie point is A; With

An alternating current-direct current separative element, comprises capacitor C _1b, wherein, C _1bone end be connected with tie point A, C _1bother end ground connection; With

A supply voltage polarization converting unit, comprises metal-oxide-semiconductor M _1b, metal-oxide-semiconductor M _2b, metal-oxide-semiconductor M _3b, metal-oxide-semiconductor M _4b, inverter INV, oscillator OSC, capacitor C _2b, capacitor C _3b, wherein, the output V of OSC _oSCoutwith M ₁grid, M _3bgrid, M _4bgrid, the input V of INV _iNVinlink together, the output V of INV _iNVoutwith M _2bgrid link together, M _4bdrain electrode meet power supply V _cC, M _4bsource electrode and M ₃drain electrode, C _3bone end link together, tie point is B, M _2bsource electrode and M _1bdrain electrode, C _3bthe other end link together, tie point is C, M _1bsource electrode and C _2bone end be connected, tie point is A, M _2bgrounded drain, M _3bsource electrode and capacitor C _2bthe other end link together, and ground connection.

2. a kind of low-voltage darlington amplifier according to claim 1, the outside direct current biasing of described low-voltage darlington amplifier, contains:

A biasing resistor R _bias, a choke induction L _chokewith a shunt capacitance C _bypass, wherein, L _chokeone end and low-voltage darlington amplifier output V _oUTconnect L _chokethe other end and R _biasand Cb _ypassone end be connected, C _bypassother end ground connection, R _biasthe other end be connected with power supply.