Amplifiers – With semiconductor amplifying device – Including differential amplifier
Patent
1996-07-19
1999-02-23
Mottola, Steven
Amplifiers
With semiconductor amplifying device
Including differential amplifier
327359, H03F 345
Patent
active
058748571
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND
It is known to use a multiplier for gain control. The control signal is applied to one input of the multiplier and the input signal is applied to the second input of the multiplier. The output signal is present at the output.
In the case of known gain control, the output signal is linear with respect to the control signal. Given an input signal of 1 volt and a control signal between 0 and 10 volts, it is possible to realize linear gain properties having factors between 0 and 100. That is to say that a gain factor of 100 is produced for a control signal of 10 volts, and for a control signal of 5 volts the gain factor is 50. If the gain factors are expressed in dB, the gain factor of 100 corresponds to a value of 40 dB and the gain factor of 50 corresponds to the value 34 dB. A linear amplifier is therefore unsuitable for dB linearity, since the changes in the output signal have a great effect in the lower control ranges whereas, in the upper control ranges, the changes in the controlled variable do not have much of an effect on the output signal.
The gain factors lie between the values 1 and 1000 in the IF range. These gain factors must be distributed uniformly over the control voltage, and dB linearity between the output voltage and the control signal is therefore to be aimed at.
It is furthermore known from U.S. Pat. No. 5,057,717 and U.S. Pat. No. 4,004,141 to change an output voltage as a logarithmic function of the input voltage.
SUMMARY OF THE INVENTION
The invention is based on the object of designing a controlled multiplying amplifier to be dB linear.
According to the invention, the inputs of the multiplying amplifier have transistors connected upstream of them for drive purposes. These transistors are to be equated with transistor areas on a chip. If the number of upstream transistors or transistor areas upstream of each input of the multiplier is selected to be identical, the multiplier operates linearly. If the number of transistors or transistor areas upstream of the inputs is selected to be different, then dB linearization is possible given a suitable distribution ratio of the transistors or transistor area ratios.
By controlling the current which is fed via the transistors to the inputs of the multiplier, the dB linearity can be set precisely. The appropriate distribution ratio of the transistors and thus a suitable current control can be determined by means of the series expansion.
A control unit is used to convert the control voltage into a current, on the one hand, and to compensate for temperature effects, on the other hand. The control unit has a constant component which ensures a minimum gain of 1.
The best dB linearization possible is produced with the transistor distribution ratio of 1:5. What is advantageous with this circuit is that dB linearization is made possible at low cost.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention is explained below with reference to the drawings, in which:
FIG. 1 shows a circuit constructed according to the invention,
FIG. 2 shows the characteristic obtained with the circuit according to FIG. 1,
FIG. 3 shows a development of the circuit constructed according to the invention, and
FIGS. 4,5,6,7,8,9,10 and 11 show developments of the circuit constructed according to the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 1 shows a dB-linearized multiplier. The IF voltage UE is converted into the current IE by means of a voltage/current converter 1, which is formed by the transistors T11, T12 and the resistors RE. The current IE is drawn off by the upper multiplier 2. A DC signal U2 is present at the inputs of the multiplier 2. The output voltage VC is present at the output of the multiplier 2. The DC U1 is present at the base of the transistors T1, T2, T3, T4, T5, T6. The DC signal U2 changes its value as a function of the currents Ia, Ib. The control unit 3 converts the control voltage VAGC into the currents Ia and Ib. The current Ia is drawn off by the transistor T1 depending on the control unit 3. The current Ib is dra
REFERENCES:
patent: 4004141 (1977-01-01), Curtis
patent: 4429416 (1984-01-01), Page
patent: 5057717 (1991-10-01), Kimura
patent: 5589791 (1996-12-01), Gilbert
Rieger Martin
Roth Sabine
Deutsche Thomson Brandt GmbH
Emanuel Peter M.
Mottola Steven
Tripoli Joseph S.
Wein Frederick A.
LandOfFree
Amplifier stage with dB-linear output voltage does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Amplifier stage with dB-linear output voltage, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Amplifier stage with dB-linear output voltage will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-310565