To obtain the required accuracy of the six most significant binary weighted bit currents, dynamic element matching is used. The reference current is divided into four nearly equal parts by means of a passive current divider using resistor matching. The four currents are interchanged during equal time intervals controlled by an internal shift register.
The output currents of this dynamic divider stage alll have the same average value with a relative error which ecluals the resistor matching accuracy times the timing accuracy of the interchanging network. A more complete description of dynamic current division is provided in [4]. Two of these interchanged currents are added to construct the most significant bit current. The third one is fed directly to the bit switches, while the fourth current flows through a second identical dynamic stage.
Three of these dynamic divider stages are needed to construct the six MSB currents. The interchanging network consists of Darlington differential pairs which are optimized for base current losses and interchanging frequency. The clock frequency of the interchanging shift register is not related to the sample frequency and is generated by a free-running emitter-ccnpled oscillator which operates at about kHz without affecting the accuracy.
A simple low-pass filter is used to remove the ripple of the bit currents due to the interchanging operation to obtain the accuracy and is only drawn here for the MSB. This approach requires seven noncritical external ceramic cttpacitors for each channel. Furthermore, the thermal noise on the bit currents is reduced by the filtering operation down to dB below the maximum output level of the converter.
The Darlington stages isolate the filter operation from switching transients of the bit switches. One output current of the last dynaniic divider is fed to the new bit passive divider.
This concept is used for the remaining ten least significant bits. It only consists of Darlington transistors and does not require any trimming or adjustment procedure and operates over a large temperature range.
In this way the input current I in is divided into equal currents with a value of one LSB. The output current of the MSB bit of this passive divider is constructed by a combination of collector currents. The required accuracy can only be obtained by carefully randomizing the transistors over the passive current divider surface to eliminate temperature gradients and to minimize mask errors.
Assuming a Gaussian distribution between the offset voltages of the transistors, the relative accuracy of the coflector current improves, according to statistics, with the square root of the number of transistor pairs involved.
In an N -bit passive current divider the required accuracy is given by. The bit switches are optimized for fast-settling and lowglitch current to avoid the need of extra sample-and-hold or deglitcher circuitry. Due to offset-binary coding, the largest glitch occurs at the zero crossing of the analog output signal. The charge of one glitch is given by the expression.
To avoid differences in base current losses owing to the different bit currents, the six most significant bits are switched with a fast diode-transistor switch, as is shown in Fig. The diode-transistor switch is controlled by data latches and driven by a differential amplifier.
At the emitter node of the switch a voltage swing of half the collector swing is present. To avoid long settling times due to the parasitic load Z out , a cascode stage is added. To further minimize this parasitic load and to preserve the current generation network from switching transients, an extra cascode stage is added. The next four bit currents are switched with compensated diode-transistor switches, as shown in Fig. This compensation is added to cancel the voltage swing at the current source connection which causes long settling times as these bit currents are small to discharge the parasitic capacitors.
When the bit current is drained to V ref, an extra current I comp is added to the current source connection and this causes an extra voltage drop over the resistor R , which cancels the voltage swing at the emitter node. During switching transients a small amount of compensation current flows into the output line of the converter.
An error in the bit current could be introduced depending on the magnitude of the compensation current and the time duration of the current transient. The charge contribution of this current transient can be compared with the charge contribution of one LSB current during one sample period. The compensation current in the bit switch has about the same magnitude as the bit current itself. For bit number N the current I comp can be written as. To avoid large glitches in the output current this switching method is not used for the six most significant bits.
The six least significant bits are switched to the output line with differential pairs, which are compensated for base current losses. Normally an operational amplifier will be applied for this purpose. To allow an easy interfacing between various digital signal processing devices operating at different word lengths, two different data input formats can be used. This standard provides an easy interfacing between digital signal processing devices, operating at various word lengths.
In this standard three signals are used. The first one is the DATA signal. It consists of a sample of the right channell followed by a sample of the left channel.
Any bit length is allowed although the MSB must be the first one. It is not only used to clock the DATA bits into the input latches, but also to determine exactly the moment at which the sample value appears at the output. In this mode the DATA signals of the left and right channel are applied simultaneously to two different input pins.
Only one bit clock signal is used to clock both data signals into the converter. The positive slope of the latch enable signal is used to indicate the end of the data input action and to determine the moment at which the outputs change their sample values.
This input format is especially suited for those cases in whi;h the circuits in front of the DAC use a nonstandard serial format.
The circuit is processed in a standard bipolar technology with double-sided isolation and double-layer interconnection. You are now ready to convert video. Hit convert, the convert shall begin immediately.
Wait patiently till the process is complete. YTD Video Downloader. Adobe Photoshop CC. VirtualDJ Avast Free Security. WhatsApp Messenger. Talking Tom Cat. Clash of Clans. Subway Surfers. TubeMate 3. Raising the Nyquist frequency also relaxes the requirements for the analog low-pass filter, reducing its negative effects on the audioband.
If you were to output a sinewave from a NOS DAC, you might be reminded of a ziggurat, or an old video game or Minecraft in which all lines are either horizontal or vertical. To me, at least, it looks far worse than it sounds. The advantage is, essentially, perfect impulse response with no ringing. The main disadvantage of a NOS DAC is that it will not remove signal aliases above the Nyquist frequency without a very steep analog low-pass filter.
On their website Denafrips talks a lot about the musical superiority of their non-oversampling mode, and nothing much about their oversampling modes. I did all of my critical listening in NOS mode because I found the sound, overall, more pleasant. I used a variety of gear during my time with the Denafrips Ares II, and found in some of those pairings that its high output impedance affected the sound.
The other line-level inputs in the Tandberg have a nice, high input impedance of k ohms. I tried both, because the Ares II produced some interesting results into the Kinki when the input impedance dropped. In a word, it sounded natural. The same is true for OS mode, but for different reasons mainly filter ringing.
Fortunately, our brains are pretty adept computers that can adapt to a lot of things. Some of this is inherent to the NOS output but it rolls off more than calculus alone can explain.
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